209728997 has 4 divisors (see below), whose sum is σ = 209811756. Its totient is φ = 209646240.

The previous prime is 209728979. The next prime is 209728999. The reversal of 209728997 is 799827902.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 799827902 = 2 ⋅399913951.

It can be written as a sum of positive squares in 2 ways, for example, as 155102116 + 54626881 = 12454^2 + 7391^2 .

It is a cyclic number.

It is not a de Polignac number, because 209728997 - 2⁶ = 209728933 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209728999) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 37454 + ... + 42687.

It is an arithmetic number, because the mean of its divisors is an integer number (52452939).

Almost surely, 2^209728997 is an apocalyptic number.

It is an amenable number.

209728997 is a deficient number, since it is larger than the sum of its proper divisors (82759).

209728997 is an equidigital number, since it uses as much as digits as its factorization.

209728997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82758.

The product of its (nonzero) digits is 1143072, while the sum is 53.

The square root of 209728997 is about 14482.0232357223. The cubic root of 209728997 is about 594.1363993883.

The spelling of 209728997 in words is "two hundred nine million, seven hundred twenty-eight thousand, nine hundred ninety-seven".