77995612021 has 4 divisors (see below), whose sum is σ = 78219095500. Its totient is φ = 77772128544.

The previous prime is 77995611983. The next prime is 77995612073. The reversal of 77995612021 is 12021659977.

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 51479072100 + 26516539921 = 226890^2 + 162839^2 .

It is a cyclic number.

It is not a de Polignac number, because 77995612021 - 2⁹ = 77995611509 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (77995613021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 111741216 + ... + 111741913.

It is an arithmetic number, because the mean of its divisors is an integer number (19554773875).

Almost surely, 2^77995612021 is an apocalyptic number.

It is an amenable number.

77995612021 is a deficient number, since it is larger than the sum of its proper divisors (223483479).

77995612021 is a wasteful number, since it uses less digits than its factorization.

77995612021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 223483478.

The product of its (nonzero) digits is 476280, while the sum is 49.

The spelling of 77995612021 in words is "seventy-seven billion, nine hundred ninety-five million, six hundred twelve thousand, twenty-one".