21512939 has 16 divisors (see below), whose sum is σ = 26163648. Its totient is φ = 17267712.

The previous prime is 21512917. The next prime is 21512941. The reversal of 21512939 is 93921512.

It is not a de Polignac number, because 21512939 - 2²⁰ = 20464363 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21512969) 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 15 ways as a sum of consecutive naturals, for example, 34559 + ... + 35175.

It is an arithmetic number, because the mean of its divisors is an integer number (1635228).

Almost surely, 2^21512939 is an apocalyptic number.

21512939 is a deficient number, since it is larger than the sum of its proper divisors (4650709).

21512939 is a wasteful number, since it uses less digits than its factorization.

21512939 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 934.

The product of its digits is 4860, while the sum is 32.

The square root of 21512939 is about 4638.2042861435. The cubic root of 21512939 is about 278.1206582498.

The spelling of 21512939 in words is "twenty-one million, five hundred twelve thousand, nine hundred thirty-nine".