78512021 has 4 divisors (see below), whose sum is σ = 89728032. Its totient is φ = 67296012.

The previous prime is 78512003. The next prime is 78512029. The reversal of 78512021 is 12021587.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12021587 = 3257 ⋅3691.

It is not a de Polignac number, because 78512021 - 2⁶ = 78511957 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 (78512029) 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, 5607995 + ... + 5608008.

It is an arithmetic number, because the mean of its divisors is an integer number (22432008).

Almost surely, 2^78512021 is an apocalyptic number.

It is an amenable number.

78512021 is a deficient number, since it is larger than the sum of its proper divisors (11216011).

78512021 is a wasteful number, since it uses less digits than its factorization.

78512021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11216010.

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 78512021 is about 8860.7009316419. The cubic root of 78512021 is about 428.1987405686.

The spelling of 78512021 in words is "seventy-eight million, five hundred twelve thousand, twenty-one".