21972428 has 24 divisors (see below), whose sum is σ = 40212480. Its totient is φ = 10492560.

The previous prime is 21972421. The next prime is 21972437. The reversal of 21972428 is 82427912.

It is a Smith number, since the sum of its digits (35) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21972421) 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 7 ways as a sum of consecutive naturals, for example, 8675 + ... + 10917.

It is an arithmetic number, because the mean of its divisors is an integer number (1675520).

Almost surely, 2^21972428 is an apocalyptic number.

It is an amenable number.

21972428 is a deficient number, since it is larger than the sum of its proper divisors (18240052).

21972428 is a wasteful number, since it uses less digits than its factorization.

21972428 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2357 (or 2355 counting only the distinct ones).

The product of its digits is 16128, while the sum is 35.

The square root of 21972428 is about 4687.4756532701. The cubic root of 21972428 is about 280.0868268141.

The spelling of 21972428 in words is "twenty-one million, nine hundred seventy-two thousand, four hundred twenty-eight".