78264721 has 4 divisors (see below), whose sum is σ = 78283444. Its totient is φ = 78246000.

The previous prime is 78264713. The next prime is 78264727. The reversal of 78264721 is 12746287.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12746287 = 113 ⋅112799.

It can be written as a sum of positive squares in 2 ways, for example, as 65044225 + 13220496 = 8065^2 + 3636^2 .

It is a cyclic number.

It is not a de Polignac number, because 78264721 - 2³ = 78264713 is a prime.

It is a super-2 number, since 2×78264721² = 12250733106415682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78264727) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 91 + ... + 12511.

It is an arithmetic number, because the mean of its divisors is an integer number (19570861).

Almost surely, 2^78264721 is an apocalyptic number.

It is an amenable number.

78264721 is a deficient number, since it is larger than the sum of its proper divisors (18723).

78264721 is a wasteful number, since it uses less digits than its factorization.

78264721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18722.

The product of its digits is 37632, while the sum is 37.

The square root of 78264721 is about 8846.7350474624. The cubic root of 78264721 is about 427.7486824136.

The spelling of 78264721 in words is "seventy-eight million, two hundred sixty-four thousand, seven hundred twenty-one".