72221921 has 2 divisors, whose sum is σ = 72221922. Its totient is φ = 72221920.

The previous prime is 72221917. The next prime is 72221923. The reversal of 72221921 is 12912227.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 62236321 + 9985600 = 7889^2 + 3160^2 .

It is a cyclic number.

It is not a de Polignac number, because 72221921 - 2² = 72221917 is a prime.

Together with 72221923, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (72221923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36110960 + 36110961.

It is an arithmetic number, because the mean of its divisors is an integer number (36110961).

Almost surely, 2^72221921 is an apocalyptic number.

It is an amenable number.

72221921 is a deficient number, since it is larger than the sum of its proper divisors (1).

72221921 is an equidigital number, since it uses as much as digits as its factorization.

72221921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1008, while the sum is 26.

The square root of 72221921 is about 8498.3481336081. The cubic root of 72221921 is about 416.4437468553.

The spelling of 72221921 in words is "seventy-two million, two hundred twenty-one thousand, nine hundred twenty-one".