72157121 has 2 divisors, whose sum is σ = 72157122. Its totient is φ = 72157120.

The previous prime is 72157109. The next prime is 72157159. The reversal of 72157121 is 12175127.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 71233600 + 923521 = 8440^2 + 961^2 .

It is an emirp because it is prime and its reverse (12175127) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-72157121 is a prime.

It is a super-2 number, since 2×72157121² = 10413300222017282, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (72157321) 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 as a sum of consecutive naturals, namely, 36078560 + 36078561.

It is an arithmetic number, because the mean of its divisors is an integer number (36078561).

Almost surely, 2^72157121 is an apocalyptic number.

It is an amenable number.

72157121 is a deficient number, since it is larger than the sum of its proper divisors (1).

72157121 is an equidigital number, since it uses as much as digits as its factorization.

72157121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 980, while the sum is 26.

The square root of 72157121 is about 8494.5347724287. The cubic root of 72157121 is about 416.3191603528.

The spelling of 72157121 in words is "seventy-two million, one hundred fifty-seven thousand, one hundred twenty-one".