78979981 has 4 divisors (see below), whose sum is σ = 80906364. Its totient is φ = 77053600.

The previous prime is 78979973. The next prime is 78979987. The reversal of 78979981 is 18997987.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18997987 = 29 ⋅655103.

It can be written as a sum of positive squares in 2 ways, for example, as 30802500 + 48177481 = 5550^2 + 6941^2 .

It is a cyclic number.

It is not a de Polignac number, because 78979981 - 2³ = 78979973 is a prime.

It is a super-2 number, since 2×78979981² = 12475674797520722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78979987) 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 3 ways as a sum of consecutive naturals, for example, 963130 + ... + 963211.

It is an arithmetic number, because the mean of its divisors is an integer number (20226591).

Almost surely, 2^78979981 is an apocalyptic number.

It is an amenable number.

78979981 is a deficient number, since it is larger than the sum of its proper divisors (1926383).

78979981 is a wasteful number, since it uses less digits than its factorization.

78979981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1926382.

The product of its digits is 2286144, while the sum is 58.

The square root of 78979981 is about 8887.0681892287. The cubic root of 78979981 is about 429.0477956177.

The spelling of 78979981 in words is "seventy-eight million, nine hundred seventy-nine thousand, nine hundred eighty-one".