21057079 has 4 divisors (see below), whose sum is σ = 21066760. Its totient is φ = 21047400.

The previous prime is 21057061. The next prime is 21057083. The reversal of 21057079 is 97075012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21057079 - 2⁷ = 21056951 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21057079.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21057019) 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, 112 + ... + 6490.

It is an arithmetic number, because the mean of its divisors is an integer number (5266690).

Almost surely, 2^21057079 is an apocalyptic number.

21057079 is a deficient number, since it is larger than the sum of its proper divisors (9681).

21057079 is an equidigital number, since it uses as much as digits as its factorization.

21057079 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9680.

The product of its (nonzero) digits is 4410, while the sum is 31.

The square root of 21057079 is about 4588.7992982914. The cubic root of 21057079 is about 276.1421544187.

The spelling of 21057079 in words is "twenty-one million, fifty-seven thousand, seventy-nine".