79621781 has 4 divisors (see below), whose sum is σ = 80394912. Its totient is φ = 78848652.

The previous prime is 79621777. The next prime is 79621793. The reversal of 79621781 is 18712697.

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: 18712697 = 43 ⋅435179.

It is a cyclic number.

It is not a de Polignac number, because 79621781 - 2² = 79621777 is a prime.

It is a super-2 number, since 2×79621781² = 12679256019223922, 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 (79611781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 386411 + ... + 386616.

It is an arithmetic number, because the mean of its divisors is an integer number (20098728).

Almost surely, 2^79621781 is an apocalyptic number.

It is an amenable number.

79621781 is a deficient number, since it is larger than the sum of its proper divisors (773131).

79621781 is a wasteful number, since it uses less digits than its factorization.

79621781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 773130.

The product of its digits is 42336, while the sum is 41.

The square root of 79621781 is about 8923.1037761532. The cubic root of 79621781 is about 430.2068249673.

The spelling of 79621781 in words is "seventy-nine million, six hundred twenty-one thousand, seven hundred eighty-one".