77977021 has 4 divisors (see below), whose sum is σ = 77996412. Its totient is φ = 77957632.

The previous prime is 77977013. The next prime is 77977037. The reversal of 77977021 is 12077977.

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 5062500 + 72914521 = 2250^2 + 8539^2 .

It is a cyclic number.

It is not a de Polignac number, because 77977021 - 2³ = 77977013 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 (77977001) 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, 1156 + ... + 12541.

It is an arithmetic number, because the mean of its divisors is an integer number (19499103).

Almost surely, 2^77977021 is an apocalyptic number.

It is an amenable number.

77977021 is a deficient number, since it is larger than the sum of its proper divisors (19391).

77977021 is a wasteful number, since it uses less digits than its factorization.

77977021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19390.

The product of its (nonzero) digits is 43218, while the sum is 40.

The square root of 77977021 is about 8830.4598408010. The cubic root of 77977021 is about 427.2239061754.

The spelling of 77977021 in words is "seventy-seven million, nine hundred seventy-seven thousand, twenty-one".