21491164 has 24 divisors (see below), whose sum is σ = 38329200. Its totient is φ = 10542336.

The previous prime is 21491149. The next prime is 21491189. The reversal of 21491164 is 46119412.

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, 63604 + ... + 63940.

It is an arithmetic number, because the mean of its divisors is an integer number (1597050).

Almost surely, 2^21491164 is an apocalyptic number.

It is an amenable number.

21491164 is a deficient number, since it is larger than the sum of its proper divisors (16838036).

21491164 is a wasteful number, since it uses less digits than its factorization.

21491164 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 597 (or 595 counting only the distinct ones).

The product of its digits is 1728, while the sum is 28.

The square root of 21491164 is about 4635.8563394480. The cubic root of 21491164 is about 278.0267903723.

It can be divided in two parts, 214 and 91164, that added together give a triangular number (91378 = T₄₂₇).

The spelling of 21491164 in words is "twenty-one million, four hundred ninety-one thousand, one hundred sixty-four".