78221979 has 12 divisors (see below), whose sum is σ = 123259032. Its totient is φ = 47407200.

The previous prime is 78221971. The next prime is 78221989. The reversal of 78221979 is 97912287.

It is not a de Polignac number, because 78221979 - 2³ = 78221971 is a prime.

It is a super-2 number, since 2×78221979² = 12237355997352882, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (78221971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 394962 + ... + 395159.

It is an arithmetic number, because the mean of its divisors is an integer number (10271586).

Almost surely, 2^78221979 is an apocalyptic number.

78221979 is a deficient number, since it is larger than the sum of its proper divisors (45037053).

78221979 is a wasteful number, since it uses less digits than its factorization.

78221979 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 790138 (or 790135 counting only the distinct ones).

The product of its digits is 127008, while the sum is 45.

The square root of 78221979 is about 8844.3190240968. The cubic root of 78221979 is about 427.6708007356.

It can be divided in two parts, 7822 and 1979, that added together give a square (9801 = 99²).

The spelling of 78221979 in words is "seventy-eight million, two hundred twenty-one thousand, nine hundred seventy-nine".