21008057 has 4 divisors (see below), whose sum is σ = 24009216. Its totient is φ = 18006900.

The previous prime is 21008041. The next prime is 21008081. The reversal of 21008057 is 75080012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21008057 - 2⁴ = 21008041 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21008027) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1500569 + ... + 1500582.

It is an arithmetic number, because the mean of its divisors is an integer number (6002304).

Almost surely, 2^21008057 is an apocalyptic number.

It is an amenable number.

21008057 is a deficient number, since it is larger than the sum of its proper divisors (3001159).

21008057 is an equidigital number, since it uses as much as digits as its factorization.

21008057 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3001158.

The product of its (nonzero) digits is 560, while the sum is 23.

The square root of 21008057 is about 4583.4547014234. The cubic root of 21008057 is about 275.9276967014.

Adding to 21008057 its reverse (75080012), we get a palindrome (96088069).

The spelling of 21008057 in words is "twenty-one million, eight thousand, fifty-seven".