21512390 has 16 divisors (see below), whose sum is σ = 38888640. Its totient is φ = 8568000.

The previous prime is 21512371. The next prime is 21512401. The reversal of 21512390 is 9321512.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2111 + ... + 6890.

It is an arithmetic number, because the mean of its divisors is an integer number (2430540).

Almost surely, 2^21512390 is an apocalyptic number.

21512390 is a deficient number, since it is larger than the sum of its proper divisors (17376250).

21512390 is a wasteful number, since it uses less digits than its factorization.

21512390 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9247.

The product of its (nonzero) digits is 540, while the sum is 23.

The square root of 21512390 is about 4638.1451033792. The cubic root of 21512390 is about 278.1182923939.

The spelling of 21512390 in words is "twenty-one million, five hundred twelve thousand, three hundred ninety".