77920961 has 4 divisors (see below), whose sum is σ = 78210900. Its totient is φ = 77631024.

The previous prime is 77920903. The next prime is 77920991. The reversal of 77920961 is 16902977.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 46840336 + 31080625 = 6844^2 + 5575^2 .

It is a cyclic number.

It is not a de Polignac number, because 77920961 - 2⁶ = 77920897 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (77920991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 144566 + ... + 145103.

It is an arithmetic number, because the mean of its divisors is an integer number (19552725).

Almost surely, 2^77920961 is an apocalyptic number.

It is an amenable number.

77920961 is a deficient number, since it is larger than the sum of its proper divisors (289939).

77920961 is a wasteful number, since it uses less digits than its factorization.

77920961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 289938.

The product of its (nonzero) digits is 47628, while the sum is 41.

The square root of 77920961 is about 8827.2850299512. The cubic root of 77920961 is about 427.1215003056.

The spelling of 77920961 in words is "seventy-seven million, nine hundred twenty thousand, nine hundred sixty-one".