21801572 has 12 divisors (see below), whose sum is σ = 41087676. Its totient is φ = 10062240.

The previous prime is 21801553. The next prime is 21801581. The reversal of 21801572 is 27510812.

It can be written as a sum of positive squares in 2 ways, for example, as 8726116 + 13075456 = 2954^2 + 3616^2 .

It is a Harshad number since it is a multiple of its sum of digits (26).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 209579 + ... + 209682.

It is an arithmetic number, because the mean of its divisors is an integer number (3423973).

Almost surely, 2^21801572 is an apocalyptic number.

It is an amenable number.

21801572 is a deficient number, since it is larger than the sum of its proper divisors (19286104).

21801572 is a wasteful number, since it uses less digits than its factorization.

21801572 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 419278 (or 419276 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 21801572 is about 4669.2153516410. The cubic root of 21801572 is about 279.3589586687.

The spelling of 21801572 in words is "twenty-one million, eight hundred one thousand, five hundred seventy-two".