21757872 has 20 divisors (see below), whose sum is σ = 56207960. Its totient is φ = 7252608.

The previous prime is 21757849. The next prime is 21757873. The reversal of 21757872 is 27875712.

It is a self number, because there is not a number n which added to its sum of digits gives 21757872.

It is not an unprimeable number, because it can be changed into a prime (21757873) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 226597 + ... + 226692.

It is an arithmetic number, because the mean of its divisors is an integer number (2810398).

Almost surely, 2^21757872 is an apocalyptic number.

It is an amenable number.

21757872 is an abundant number, since it is smaller than the sum of its proper divisors (34450088).

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

21757872 is a wasteful number, since it uses less digits than its factorization.

21757872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 453300 (or 453294 counting only the distinct ones).

The product of its digits is 54880, while the sum is 39.

The square root of 21757872 is about 4664.5334171812. The cubic root of 21757872 is about 279.1721808173.

The spelling of 21757872 in words is "twenty-one million, seven hundred fifty-seven thousand, eight hundred seventy-two".