209399971894281 has 45 divisors (see below), whose sum is σ = 363879539894871. Its totient is φ = 119656605853008.

The previous prime is 209399971894279. The next prime is 209399971894349. The reversal of 209399971894281 is 182498179993902.

It is a happy number.

The square root of 209399971894281 is 14470659.

It is a perfect power (a square), and thus also a powerful number.

209399971894281 is a `hidden beast` number, since 2 + 0 + 9 + 3 + 9 + 9 + 9 + 7 + 189 + 428 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 30120833180025 + 179279138714256 = 5488245^2 + 13389516^2 .

It is not a de Polignac number, because 209399971894281 - 2¹ = 209399971894279 is a prime.

It is a super-2 number, since 2×209399971894281² (a number of 29 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (81).

It is a self number, because there is not a number n which added to its sum of digits gives 209399971894281.

It is not an unprimeable number, because it can be changed into a prime (209399971894081) by changing a digit.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 911536671 + ... + 911766363.

Almost surely, 2^{209399971894281} is an apocalyptic number.

209399971894281 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

209399971894281 is the 14470659-th square number.

209399971894281 is the 7235330-th centered octagonal number.

It is an amenable number.

209399971894281 is a deficient number, since it is larger than the sum of its proper divisors (154479568000590).

209399971894281 is an frugal number, since it uses more digits than its factorization.

209399971894281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 459412 (or 229703 counting only the distinct ones).

The product of its (nonzero) digits is 1269789696, while the sum is 81.

209399971894281 divided by its sum of digits (81) gives a square (2585184838201 = 1607851²).

The spelling of 209399971894281 in words is "two hundred nine trillion, three hundred ninety-nine billion, nine hundred seventy-one million, eight hundred ninety-four thousand, two hundred eighty-one".