77756421 has 4 divisors (see below), whose sum is σ = 103675232. Its totient is φ = 51837612.

The previous prime is 77756411. The next prime is 77756423. The reversal of 77756421 is 12465777.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 77756421 - 2⁵ = 77756389 is a prime.

It is a super-2 number, since 2×77756421² = 12092122013458482, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 77756421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (77756423) 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, 12959401 + ... + 12959406.

It is an arithmetic number, because the mean of its divisors is an integer number (25918808).

Almost surely, 2^77756421 is an apocalyptic number.

It is an amenable number.

77756421 is a deficient number, since it is larger than the sum of its proper divisors (25918811).

77756421 is a wasteful number, since it uses less digits than its factorization.

77756421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25918810.

The product of its digits is 82320, while the sum is 39.

The square root of 77756421 is about 8817.9601382633. The cubic root of 77756421 is about 426.8206480221.

It can be divided in two parts, 7775 and 6421, that added together give a triangular number (14196 = T₁₆₈).

The spelling of 77756421 in words is "seventy-seven million, seven hundred fifty-six thousand, four hundred twenty-one".