78342721 has 2 divisors, whose sum is σ = 78342722. Its totient is φ = 78342720.

The previous prime is 78342707. The next prime is 78342743. The reversal of 78342721 is 12724387.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 76755121 + 1587600 = 8761^2 + 1260^2 .

It is a cyclic number.

It is not a de Polignac number, because 78342721 - 2¹⁷ = 78211649 is a prime.

It is a super-2 number, since 2×78342721² = 12275163867367682, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (78342701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39171360 + 39171361.

It is an arithmetic number, because the mean of its divisors is an integer number (39171361).

Almost surely, 2^78342721 is an apocalyptic number.

It is an amenable number.

78342721 is a deficient number, since it is larger than the sum of its proper divisors (1).

78342721 is an equidigital number, since it uses as much as digits as its factorization.

78342721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18816, while the sum is 34.

The square root of 78342721 is about 8851.1423556510. The cubic root of 78342721 is about 427.8907358577.

The spelling of 78342721 in words is "seventy-eight million, three hundred forty-two thousand, seven hundred twenty-one".