21972173 has 2 divisors, whose sum is σ = 21972174. Its totient is φ = 21972172.

The previous prime is 21972127. The next prime is 21972217. The reversal of 21972173 is 37127912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18335524 + 3636649 = 4282^2 + 1907^2 .

It is a cyclic number.

It is not a de Polignac number, because 21972173 - 2¹⁰ = 21971149 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21972073) 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 as a sum of consecutive naturals, namely, 10986086 + 10986087.

It is an arithmetic number, because the mean of its divisors is an integer number (10986087).

Almost surely, 2^21972173 is an apocalyptic number.

It is an amenable number.

21972173 is a deficient number, since it is larger than the sum of its proper divisors (1).

21972173 is an equidigital number, since it uses as much as digits as its factorization.

21972173 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5292, while the sum is 32.

The square root of 21972173 is about 4687.4484530499. The cubic root of 21972173 is about 280.0857432983.

The spelling of 21972173 in words is "twenty-one million, nine hundred seventy-two thousand, one hundred seventy-three".