21863664 has 60 divisors (see below), whose sum is σ = 61659000. Its totient is φ = 7231872.

The previous prime is 21863657. The next prime is 21863671. The reversal of 21863664 is 46636812.

21863664 is a `hidden beast` number, since 2 + 18 + 636 + 6 + 4 = 666.

It is an interprime number because it is at equal distance from previous prime (21863657) and next prime (21863671).

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

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 20947 + ... + 21965.

It is an arithmetic number, because the mean of its divisors is an integer number (1027650).

Almost surely, 2^21863664 is an apocalyptic number.

21863664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21863664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30829500).

21863664 is an abundant number, since it is smaller than the sum of its proper divisors (39795336).

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

21863664 is a wasteful number, since it uses less digits than its factorization.

21863664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1182 (or 1173 counting only the distinct ones).

The product of its digits is 41472, while the sum is 36.

The square root of 21863664 is about 4675.8597070485. The cubic root of 21863664 is about 279.6239168573.

The spelling of 21863664 in words is "twenty-one million, eight hundred sixty-three thousand, six hundred sixty-four".