21972237 has 32 divisors (see below), whose sum is σ = 34636800. Its totient is φ = 12383280.

The previous prime is 21972229. The next prime is 21972241. The reversal of 21972237 is 73227912.

It is not a de Polignac number, because 21972237 - 2³ = 21972229 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21972198 and 21972207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21972217) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 134718 + ... + 134880.

It is an arithmetic number, because the mean of its divisors is an integer number (1082400).

Almost surely, 2^21972237 is an apocalyptic number.

It is an amenable number.

21972237 is a deficient number, since it is larger than the sum of its proper divisors (12664563).

21972237 is a wasteful number, since it uses less digits than its factorization.

21972237 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 318 (or 304 counting only the distinct ones).

The product of its digits is 10584, while the sum is 33.

The square root of 21972237 is about 4687.4552797867. The cubic root of 21972237 is about 280.0860152403.

The spelling of 21972237 in words is "twenty-one million, nine hundred seventy-two thousand, two hundred thirty-seven".