21591316 has 24 divisors (see below), whose sum is σ = 38810016. Its totient is φ = 10506720.

The previous prime is 21591307. The next prime is 21591329. The reversal of 21591316 is 61319512.

21591316 = T₁₈ + T₁₉ + ... + T₅₀₅.

It is a super-2 number, since 2×21591316² = 932369853223712, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 25695 + ... + 26521.

It is an arithmetic number, because the mean of its divisors is an integer number (1617084).

Almost surely, 2^21591316 is an apocalyptic number.

It is an amenable number.

21591316 is a deficient number, since it is larger than the sum of its proper divisors (17218700).

21591316 is a wasteful number, since it uses less digits than its factorization.

21591316 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 999 (or 997 counting only the distinct ones).

The product of its digits is 1620, while the sum is 28.

The square root of 21591316 is about 4646.6456718799. The cubic root of 21591316 is about 278.4580032016.

It can be divided in two parts, 21 and 591316, that multiplied together give a triangular number (12417636 = T₄₉₈₃).

The spelling of 21591316 in words is "twenty-one million, five hundred ninety-one thousand, three hundred sixteen".