21809572 has 24 divisors (see below), whose sum is σ = 41023584. Its totient is φ = 10108032.

The previous prime is 21809569. The next prime is 21809573. The reversal of 21809572 is 27590812.

It is a Harshad number since it is a multiple of its sum of digits (34).

It is not an unprimeable number, because it can be changed into a prime (21809573) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 2163 + ... + 6949.

It is an arithmetic number, because the mean of its divisors is an integer number (1709316).

Almost surely, 2^21809572 is an apocalyptic number.

It is an amenable number.

21809572 is a deficient number, since it is larger than the sum of its proper divisors (19214012).

21809572 is a wasteful number, since it uses less digits than its factorization.

21809572 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4875 (or 4873 counting only the distinct ones).

The product of its (nonzero) digits is 10080, while the sum is 34.

The square root of 21809572 is about 4670.0719480539. The cubic root of 21809572 is about 279.3931243757.

The spelling of 21809572 in words is "twenty-one million, eight hundred nine thousand, five hundred seventy-two".