21972737 has 8 divisors (see below), whose sum is σ = 22271496. Its totient is φ = 21676032.

The previous prime is 21972733. The next prime is 21972763. The reversal of 21972737 is 73727912.

It can be written as a sum of positive squares in 4 ways, for example, as 1893376 + 20079361 = 1376^2 + 4481^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21972737 - 2² = 21972733 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21972737.

It is not an unprimeable number, because it can be changed into a prime (21972733) 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, 37793 + ... + 38369.

It is an arithmetic number, because the mean of its divisors is an integer number (2783937).

Almost surely, 2^21972737 is an apocalyptic number.

It is an amenable number.

21972737 is a deficient number, since it is larger than the sum of its proper divisors (298759).

21972737 is a wasteful number, since it uses less digits than its factorization.

21972737 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1027.

The product of its digits is 37044, while the sum is 38.

The square root of 21972737 is about 4687.5086133254. The cubic root of 21972737 is about 280.0881397690.

The spelling of 21972737 in words is "twenty-one million, nine hundred seventy-two thousand, seven hundred thirty-seven".