21972788 has 6 divisors (see below), whose sum is σ = 38452386. Its totient is φ = 10986392.

The previous prime is 21972763. The next prime is 21972803. The reversal of 21972788 is 88727912.

It can be written as a sum of positive squares in only one way, i.e., 21270544 + 702244 = 4612^2 + 838^2 .

It is a congruent number.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 2746595 + ... + 2746602.

It is an arithmetic number, because the mean of its divisors is an integer number (6408731).

Almost surely, 2^21972788 is an apocalyptic number.

It is an amenable number.

21972788 is a deficient number, since it is larger than the sum of its proper divisors (16479598).

21972788 is a wasteful number, since it uses less digits than its factorization.

21972788 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5493201 (or 5493199 counting only the distinct ones).

The product of its digits is 112896, while the sum is 44.

The square root of 21972788 is about 4687.5140533123. The cubic root of 21972788 is about 280.0883564691.

The spelling of 21972788 in words is "twenty-one million, nine hundred seventy-two thousand, seven hundred eighty-eight".