21388964 has 6 divisors (see below), whose sum is σ = 37430694. Its totient is φ = 10694480.

The previous prime is 21388957. The next prime is 21388973. The reversal of 21388964 is 46988312.

It can be written as a sum of positive squares in only one way, i.e., 21086464 + 302500 = 4592^2 + 550^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2673617 + ... + 2673624.

It is an arithmetic number, because the mean of its divisors is an integer number (6238449).

Almost surely, 2^21388964 is an apocalyptic number.

It is an amenable number.

21388964 is a deficient number, since it is larger than the sum of its proper divisors (16041730).

21388964 is a wasteful number, since it uses less digits than its factorization.

21388964 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5347245 (or 5347243 counting only the distinct ones).

The product of its digits is 82944, while the sum is 41.

The square root of 21388964 is about 4624.8204289464. The cubic root of 21388964 is about 277.5853764302.

The spelling of 21388964 in words is "twenty-one million, three hundred eighty-eight thousand, nine hundred sixty-four".