21425664 has 160 divisors (see below), whose sum is σ = 65308320. Its totient is φ = 6193152.

The previous prime is 21425659. The next prime is 21425671. The reversal of 21425664 is 46652412.

It is a hoax number, since the sum of its digits (30) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 579054 + ... + 579090.

It is an arithmetic number, because the mean of its divisors is an integer number (408177).

Almost surely, 2^21425664 is an apocalyptic number.

21425664 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 21425664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32654160).

21425664 is an abundant number, since it is smaller than the sum of its proper divisors (43882656).

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

21425664 is a wasteful number, since it uses less digits than its factorization.

21425664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 100 (or 84 counting only the distinct ones).

The product of its digits is 11520, while the sum is 30.

The square root of 21425664 is about 4628.7864500320. The cubic root of 21425664 is about 277.7440495700.

It can be divided in two parts, 214 and 25664, that added together give a triangular number (25878 = T₂₂₇).

The spelling of 21425664 in words is "twenty-one million, four hundred twenty-five thousand, six hundred sixty-four".