21723552 has 180 divisors, whose sum is σ = 70207830. Its totient is φ = 6580224.

The previous prime is 21723547. The next prime is 21723553. The reversal of 21723552 is 25532712.

It can be written as a sum of positive squares in 3 ways, for example, as 21566736 + 156816 = 4644^2 + 396^2 .

It is a super-2 number, since 2×21723552² = 943825422993408, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21723553) by changing a digit.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 749074 + ... + 749102.

Almost surely, 2^21723552 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21723552, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35103915).

21723552 is an abundant number, since it is smaller than the sum of its proper divisors (48484278).

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

21723552 is a wasteful number, since it uses less digits than its factorization.

21723552 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85 (or 51 counting only the distinct ones).

The product of its digits is 4200, while the sum is 27.

The square root of 21723552 is about 4660.8531407887. The cubic root of 21723552 is about 279.0253185487.

The spelling of 21723552 in words is "twenty-one million, seven hundred twenty-three thousand, five hundred fifty-two".