72777721 has 2 divisors, whose sum is σ = 72777722. Its totient is φ = 72777720.

The previous prime is 72777673. The next prime is 72777737. The reversal of 72777721 is 12777727.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 54834025 + 17943696 = 7405^2 + 4236^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-72777721 is a prime.

It is not a weakly prime, because it can be changed into another prime (72777781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36388860 + 36388861.

It is an arithmetic number, because the mean of its divisors is an integer number (36388861).

Almost surely, 2^72777721 is an apocalyptic number.

It is an amenable number.

72777721 is a deficient number, since it is larger than the sum of its proper divisors (1).

72777721 is an equidigital number, since it uses as much as digits as its factorization.

72777721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 67228, while the sum is 40.

The square root of 72777721 is about 8530.9859336421. The cubic root of 72777721 is about 417.5092968874.

The spelling of 72777721 in words is "seventy-two million, seven hundred seventy-seven thousand, seven hundred twenty-one".