21719664 has 50 divisors (see below), whose sum is σ = 62866760. Its totient is φ = 7239456.

The previous prime is 21719657. The next prime is 21719683. The reversal of 21719664 is 46691712.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 7084 + ... + 9675.

Almost surely, 2^21719664 is an apocalyptic number.

21719664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21719664 is an abundant number, since it is smaller than the sum of its proper divisors (41147096).

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

21719664 is a wasteful number, since it uses less digits than its factorization.

21719664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16779 (or 16764 counting only the distinct ones).

The product of its digits is 18144, while the sum is 36.

The square root of 21719664 is about 4660.4360311027. The cubic root of 21719664 is about 279.0086712532.

It can be divided in two parts, 217 and 19664, that added together give a square (19881 = 141²).

The spelling of 21719664 in words is "twenty-one million, seven hundred nineteen thousand, six hundred sixty-four".