77610721 has 4 divisors (see below), whose sum is σ = 77806612. Its totient is φ = 77414832.

The previous prime is 77610707. The next prime is 77610751. The reversal of 77610721 is 12701677.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12701677 = 41 ⋅309797.

It can be written as a sum of positive squares in 2 ways, for example, as 18490000 + 59120721 = 4300^2 + 7689^2 .

It is a cyclic number.

It is not a de Polignac number, because 77610721 - 2⁹ = 77610209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (77610751) 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, 97350 + ... + 98143.

It is an arithmetic number, because the mean of its divisors is an integer number (19451653).

Almost surely, 2^77610721 is an apocalyptic number.

It is an amenable number.

77610721 is a deficient number, since it is larger than the sum of its proper divisors (195891).

77610721 is a wasteful number, since it uses less digits than its factorization.

77610721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 195890.

The product of its (nonzero) digits is 4116, while the sum is 31.

The square root of 77610721 is about 8809.6947166176. The cubic root of 77610721 is about 426.5538891247.

The spelling of 77610721 in words is "seventy-seven million, six hundred ten thousand, seven hundred twenty-one".