915979621 has 4 divisors (see below), whose sum is σ = 916617600. Its totient is φ = 915341644.

The previous prime is 915979553. The next prime is 915979643. The reversal of 915979621 is 126979519.

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: 126979519 = 3919 ⋅32401.

It is a cyclic number.

It is not a de Polignac number, because 915979621 - 2⁹ = 915979109 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (915979651) 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, 316831 + ... + 319708.

It is an arithmetic number, because the mean of its divisors is an integer number (229154400).

Almost surely, 2^915979621 is an apocalyptic number.

It is an amenable number.

915979621 is a deficient number, since it is larger than the sum of its proper divisors (637979).

915979621 is a wasteful number, since it uses less digits than its factorization.

915979621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 637978.

The product of its digits is 306180, while the sum is 49.

The square root of 915979621 is about 30265.1552284141. The cubic root of 915979621 is about 971.1700271776.

The spelling of 915979621 in words is "nine hundred fifteen million, nine hundred seventy-nine thousand, six hundred twenty-one".