991541556 has 18 divisors (see below), whose sum is σ = 2506396802. Its totient is φ = 330513840.

The previous prime is 991541549. The next prime is 991541567. The reversal of 991541556 is 655145199.

It is a happy number.

991541556 is a `hidden beast` number, since 9 + 91 + 5 + 4 + 1 + 556 = 666.

It can be written as a sum of positive squares in only one way, i.e., 909022500 + 82519056 = 30150^2 + 9084^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a super-2 number, since 2×991541556² = 1966309314549802272, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 13771375 + ... + 13771446.

Almost surely, 2^991541556 is an apocalyptic number.

It is an amenable number.

991541556 is an abundant number, since it is smaller than the sum of its proper divisors (1514855246).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

991541556 is a wasteful number, since it uses less digits than its factorization.

991541556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27542831 (or 27542826 counting only the distinct ones).

The product of its digits is 243000, while the sum is 45.

The square root of 991541556 is about 31488.7528492317. The cubic root of 991541556 is about 997.1725316241.

The spelling of 991541556 in words is "nine hundred ninety-one million, five hundred forty-one thousand, five hundred fifty-six".