21388772 has 12 divisors (see below), whose sum is σ = 37527420. Its totient is φ = 10666656.

The previous prime is 21388769. The next prime is 21388777. The reversal of 21388772 is 27788312.

It can be written as a sum of positive squares in 2 ways, for example, as 13957696 + 7431076 = 3736^2 + 2726^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21388777) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5147 + ... + 8322.

It is an arithmetic number, because the mean of its divisors is an integer number (3127285).

Almost surely, 2^21388772 is an apocalyptic number.

It is an amenable number.

21388772 is a deficient number, since it is larger than the sum of its proper divisors (16138648).

21388772 is a wasteful number, since it uses less digits than its factorization.

21388772 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13870 (or 13868 counting only the distinct ones).

The product of its digits is 37632, while the sum is 38.

The square root of 21388772 is about 4624.7996713371. The cubic root of 21388772 is about 277.5845458375.

The spelling of 21388772 in words is "twenty-one million, three hundred eighty-eight thousand, seven hundred seventy-two".