21521964 has 12 divisors (see below), whose sum is σ = 50217944. Its totient is φ = 7173984.

The previous prime is 21521963. The next prime is 21521971. The reversal of 21521964 is 46912512.

It is a tau number, because it is divible by the number of its divisors (12).

It is not an unprimeable number, because it can be changed into a prime (21521963) 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, 896737 + ... + 896760.

Almost surely, 2^21521964 is an apocalyptic number.

It is an amenable number.

21521964 is an abundant number, since it is smaller than the sum of its proper divisors (28695980).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21521964 is a wasteful number, since it uses less digits than its factorization.

21521964 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1793504 (or 1793502 counting only the distinct ones).

The product of its digits is 4320, while the sum is 30.

The square root of 21521964 is about 4639.1770821990. The cubic root of 21521964 is about 278.1595447392.

The spelling of 21521964 in words is "twenty-one million, five hundred twenty-one thousand, nine hundred sixty-four".