79220821 has 4 divisors (see below), whose sum is σ = 79252992. Its totient is φ = 79188652.

The previous prime is 79220789. The next prime is 79220831. The reversal of 79220821 is 12802297.

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: 12802297 = 751 ⋅17047.

It is a cyclic number.

It is not a de Polignac number, because 79220821 - 2⁵ = 79220789 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 (79220831) 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, 12055 + ... + 17428.

It is an arithmetic number, because the mean of its divisors is an integer number (19813248).

Almost surely, 2^79220821 is an apocalyptic number.

It is an amenable number.

79220821 is a deficient number, since it is larger than the sum of its proper divisors (32171).

79220821 is a wasteful number, since it uses less digits than its factorization.

79220821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32170.

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 79220821 is about 8900.6079005875. The cubic root of 79220821 is about 429.4834630474.

It can be divided in two parts, 79 and 220821, that added together give a square (220900 = 470²).

The spelling of 79220821 in words is "seventy-nine million, two hundred twenty thousand, eight hundred twenty-one".