21307572 has 72 divisors (see below), whose sum is σ = 63292320. Its totient is φ = 5958720.

The previous prime is 21307553. The next prime is 21307589. The reversal of 21307572 is 27570312.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3079 + ... + 7217.

It is an arithmetic number, because the mean of its divisors is an integer number (879060).

Almost surely, 2^21307572 is an apocalyptic number.

21307572 is a gapful number since it is divisible by the number (22) 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 21307572, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31646160).

21307572 is an abundant number, since it is smaller than the sum of its proper divisors (41984748).

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

21307572 is a wasteful number, since it uses less digits than its factorization.

21307572 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4173 (or 4168 counting only the distinct ones).

The product of its (nonzero) digits is 2940, while the sum is 27.

The square root of 21307572 is about 4616.0125649742. The cubic root of 21307572 is about 277.2328278307.

Adding to 21307572 its reverse (27570312), we get a palindrome (48877884).

It can be divided in two parts, 2130 and 7572, that multiplied together give a triangular number (16128360 = T₅₆₇₉).

The spelling of 21307572 in words is "twenty-one million, three hundred seven thousand, five hundred seventy-two".