72021557 has 2 divisors, whose sum is σ = 72021558. Its totient is φ = 72021556.

The previous prime is 72021539. The next prime is 72021563. The reversal of 72021557 is 75512027.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 52432081 + 19589476 = 7241^2 + 4426^2 .

It is a cyclic number.

It is not a de Polignac number, because 72021557 - 2⁶ = 72021493 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (72021527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36010778 + 36010779.

It is an arithmetic number, because the mean of its divisors is an integer number (36010779).

Almost surely, 2^72021557 is an apocalyptic number.

It is an amenable number.

72021557 is a deficient number, since it is larger than the sum of its proper divisors (1).

72021557 is an equidigital number, since it uses as much as digits as its factorization.

72021557 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4900, while the sum is 29.

The square root of 72021557 is about 8486.5515375799. The cubic root of 72021557 is about 416.0582793258.

The spelling of 72021557 in words is "seventy-two million, twenty-one thousand, five hundred fifty-seven".