72218257921 has 2 divisors, whose sum is σ = 72218257922. Its totient is φ = 72218257920.

The previous prime is 72218257901. The next prime is 72218257963. The reversal of 72218257921 is 12975281227.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 38117095696 + 34101162225 = 195236^2 + 184665^2 .

It is an emirp because it is prime and its reverse (12975281227) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 72218257921 - 2⁹ = 72218257409 is a prime.

It is not a weakly prime, because it can be changed into another prime (72218257901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36109128960 + 36109128961.

It is an arithmetic number, because the mean of its divisors is an integer number (36109128961).

Almost surely, 2^72218257921 is an apocalyptic number.

It is an amenable number.

72218257921 is a deficient number, since it is larger than the sum of its proper divisors (1).

72218257921 is an equidigital number, since it uses as much as digits as its factorization.

72218257921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 282240, while the sum is 46.

The spelling of 72218257921 in words is "seventy-two billion, two hundred eighteen million, two hundred fifty-seven thousand, nine hundred twenty-one".