21572320 has 192 divisors, whose sum is σ = 67931136. Its totient is φ = 6266880.

The previous prime is 21572297. The next prime is 21572333. The reversal of 21572320 is 2327512.

It is a Harshad number since it is a multiple of its sum of digits (22).

It is a junction number, because it is equal to n+sod(n) for n = 21572291 and 21572300.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 209389 + ... + 209491.

It is an arithmetic number, because the mean of its divisors is an integer number (353808).

Almost surely, 2^21572320 is an apocalyptic number.

21572320 is a gapful number since it is divisible by the number (20) 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 21572320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33965568).

21572320 is an abundant number, since it is smaller than the sum of its proper divisors (46358816).

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

21572320 is a wasteful number, since it uses less digits than its factorization.

21572320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 153 (or 145 counting only the distinct ones).

The product of its (nonzero) digits is 840, while the sum is 22.

The square root of 21572320 is about 4644.6011669464. The cubic root of 21572320 is about 278.3763169619.

Adding to 21572320 its reverse (2327512), we get a palindrome (23899832).

The spelling of 21572320 in words is "twenty-one million, five hundred seventy-two thousand, three hundred twenty".