78577721 has 2 divisors, whose sum is σ = 78577722. Its totient is φ = 78577720.

The previous prime is 78577693. The next prime is 78577781. The reversal of 78577721 is 12777587.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 78570496 + 7225 = 8864^2 + 85^2 .

It is a cyclic number.

It is not a de Polignac number, because 78577721 - 2⁶ = 78577657 is a prime.

It is not a weakly prime, because it can be changed into another prime (78577781) 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, 39288860 + 39288861.

It is an arithmetic number, because the mean of its divisors is an integer number (39288861).

Almost surely, 2^78577721 is an apocalyptic number.

It is an amenable number.

78577721 is a deficient number, since it is larger than the sum of its proper divisors (1).

78577721 is an equidigital number, since it uses as much as digits as its factorization.

78577721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 192080, while the sum is 44.

The square root of 78577721 is about 8864.4075380140. The cubic root of 78577721 is about 428.3181482435.

The spelling of 78577721 in words is "seventy-eight million, five hundred seventy-seven thousand, seven hundred twenty-one".