912991921 has 4 divisors (see below), whose sum is σ = 913125744. Its totient is φ = 912858100.

The previous prime is 912991913. The next prime is 912991931. The reversal of 912991921 is 129199219.

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: 129199219 = 43 ⋅3004633.

It is a cyclic number.

It is not a de Polignac number, because 912991921 - 2³ = 912991913 is a prime.

It is a super-2 number, since 2×912991921² = 1667108495622540482, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (912991931) 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, 56095 + ... + 70516.

It is an arithmetic number, because the mean of its divisors is an integer number (228281436).

Almost surely, 2^912991921 is an apocalyptic number.

It is an amenable number.

912991921 is a deficient number, since it is larger than the sum of its proper divisors (133823).

912991921 is a wasteful number, since it uses less digits than its factorization.

912991921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133822.

The product of its digits is 26244, while the sum is 43.

The square root of 912991921 is about 30215.7561712428. The cubic root of 912991921 is about 970.1129712189.

The spelling of 912991921 in words is "nine hundred twelve million, nine hundred ninety-one thousand, nine hundred twenty-one".