21139664 has 40 divisors (see below), whose sum is σ = 50413440. Its totient is φ = 8362368.

The previous prime is 21139661. The next prime is 21139667. The reversal of 21139664 is 46693112.

It is an interprime number because it is at equal distance from previous prime (21139661) and next prime (21139667).

It is a self number, because there is not a number n which added to its sum of digits gives 21139664.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21139661) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5804 + ... + 8715.

It is an arithmetic number, because the mean of its divisors is an integer number (1260336).

Almost surely, 2^21139664 is an apocalyptic number.

It is an amenable number.

21139664 is an abundant number, since it is smaller than the sum of its proper divisors (29273776).

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

21139664 is a wasteful number, since it uses less digits than its factorization.

21139664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14547 (or 14541 counting only the distinct ones).

The product of its digits is 7776, while the sum is 32.

The square root of 21139664 is about 4597.7890338727. The cubic root of 21139664 is about 276.5026895611.

The spelling of 21139664 in words is "twenty-one million, one hundred thirty-nine thousand, six hundred sixty-four".