21165257 has 8 divisors (see below), whose sum is σ = 21470592. Its totient is φ = 20862000.

The previous prime is 21165251. The next prime is 21165271. The reversal of 21165257 is 75256112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21165257 - 2⁴ = 21165241 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21165251) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 36782 + ... + 37352.

It is an arithmetic number, because the mean of its divisors is an integer number (2683824).

Almost surely, 2^21165257 is an apocalyptic number.

It is an amenable number.

21165257 is a deficient number, since it is larger than the sum of its proper divisors (305335).

21165257 is a wasteful number, since it uses less digits than its factorization.

21165257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1039.

The product of its digits is 4200, while the sum is 29.

The square root of 21165257 is about 4600.5713775574. The cubic root of 21165257 is about 276.6142283804.

The spelling of 21165257 in words is "twenty-one million, one hundred sixty-five thousand, two hundred fifty-seven".