209490205401 has 9 divisors (see below), whose sum is σ = 302598946741. Its totient is φ = 139659221532.

The previous prime is 209490205387. The next prime is 209490205427. The reversal of 209490205401 is 104502094902.

The square root of 209490205401 is 457701.

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

209490205401 is a `hidden beast` number, since 2 + 0 + 9 + 4 + 90 + 20 + 540 + 1 = 666.

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 209490205401 - 2¹⁹ = 209489681113 is a prime.

It is a super-2 number, since 2×209490205401² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (209490205451) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1296820 + ... + 1449386.

Almost surely, 2^209490205401 is an apocalyptic number.

209490205401 is the 457701-st square number.

209490205401 is the 228851-st centered octagonal number.

It is an amenable number.

209490205401 is a deficient number, since it is larger than the sum of its proper divisors (93108741340).

209490205401 is an frugal number, since it uses more digits than its factorization.

209490205401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 305140 (or 152570 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 36.

Multiplying 209490205401 by its sum of digits (36), we get a square (7541647394436 = 2746206²).

The spelling of 209490205401 in words is "two hundred nine billion, four hundred ninety million, two hundred five thousand, four hundred one".