21165057 has 14 divisors (see below), whose sum is σ = 31734162. Its totient is φ = 14109552.

The previous prime is 21165047. The next prime is 21165077. The reversal of 21165057 is 75056112.

21165057 is a `hidden beast` number, since 2 + 1 + 1 + 650 + 5 + 7 = 666.

It can be written as a sum of positive squares in only one way, i.e., 16842816 + 4322241 = 4104^2 + 2079^2 .

It is not a de Polignac number, because 21165057 - 2⁷ = 21164929 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a self number, because there is not a number n which added to its sum of digits gives 21165057.

It is not an unprimeable number, because it can be changed into a prime (21165007) by changing a digit.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 13788 + ... + 15245.

Almost surely, 2^21165057 is an apocalyptic number.

21165057 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21165057 is a deficient number, since it is larger than the sum of its proper divisors (10569105).

21165057 is an frugal number, since it uses more digits than its factorization.

21165057 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29051 (or 29036 counting only the distinct ones).

The product of its (nonzero) digits is 2100, while the sum is 27.

The square root of 21165057 is about 4600.5496410755. The cubic root of 21165057 is about 276.6133570937.

The spelling of 21165057 in words is "twenty-one million, one hundred sixty-five thousand, fifty-seven".