991511972 has 48 divisors (see below), whose sum is σ = 1962817920. Its totient is φ = 434112000.

The previous prime is 991511951. The next prime is 991512019. The reversal of 991511972 is 279115199.

It is a Harshad number since it is a multiple of its sum of digits (44).

Its product of digits (51030) is a multiple of the sum of its prime divisors (1890).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 824972 + ... + 826172.

It is an arithmetic number, because the mean of its divisors is an integer number (40892040).

Almost surely, 2^991511972 is an apocalyptic number.

It is an amenable number.

991511972 is a deficient number, since it is larger than the sum of its proper divisors (971305948).

991511972 is a wasteful number, since it uses less digits than its factorization.

991511972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1892 (or 1890 counting only the distinct ones).

The product of its digits is 51030, while the sum is 44.

The square root of 991511972 is about 31488.2830906990. The cubic root of 991511972 is about 997.1626141895.

The spelling of 991511972 in words is "nine hundred ninety-one million, five hundred eleven thousand, nine hundred seventy-two".