77908421 has 6 divisors (see below), whose sum is σ = 80072370. Its totient is φ = 75801456.

The previous prime is 77908409. The next prime is 77908427. The reversal of 77908421 is 12480977.

It can be written as a sum of positive squares in 3 ways, for example, as 32615521 + 45292900 = 5711^2 + 6730^2 .

It is not a de Polignac number, because 77908421 - 2¹⁰ = 77907397 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 (77908427) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 27086 + ... + 29823.

It is an arithmetic number, because the mean of its divisors is an integer number (13345395).

Almost surely, 2^77908421 is an apocalyptic number.

It is an amenable number.

77908421 is a deficient number, since it is larger than the sum of its proper divisors (2163949).

77908421 is an equidigital number, since it uses as much as digits as its factorization.

77908421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56983 (or 56946 counting only the distinct ones).

The product of its (nonzero) digits is 28224, while the sum is 38.

The square root of 77908421 is about 8826.5747037002. The cubic root of 77908421 is about 427.0985865269.

The spelling of 77908421 in words is "seventy-seven million, nine hundred eight thousand, four hundred twenty-one".