21065579 has 4 divisors (see below), whose sum is σ = 21076776. Its totient is φ = 21054384.

The previous prime is 21065563. The next prime is 21065599. The reversal of 21065579 is 97556012.

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 21065579 - 2⁴ = 21065563 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21065549) 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, 2009 + ... + 6794.

It is an arithmetic number, because the mean of its divisors is an integer number (5269194).

Almost surely, 2^21065579 is an apocalyptic number.

21065579 is a deficient number, since it is larger than the sum of its proper divisors (11197).

21065579 is an equidigital number, since it uses as much as digits as its factorization.

21065579 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11196.

The product of its (nonzero) digits is 18900, while the sum is 35.

The square root of 21065579 is about 4589.7253730479. The cubic root of 21065579 is about 276.1793057025.

The spelling of 21065579 in words is "twenty-one million, sixty-five thousand, five hundred seventy-nine".