991556 has 6 divisors (see below), whose sum is σ = 1735230. Its totient is φ = 495776.

The previous prime is 991547. The next prime is 991567. The reversal of 991556 is 655199.

It can be written as a sum of positive squares in only one way, i.e., 774400 + 217156 = 880^2 + 466^2 .

It is a super-2 number, since 2×991556² = 1966366602272, which contains 22 as substring.

It is an unprimeable number.

991556 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 123941 + ... + 123948.

It is an arithmetic number, because the mean of its divisors is an integer number (289205).

2⁹⁹¹⁵⁵⁶ is an apocalyptic number.

It is an amenable number.

991556 is a deficient number, since it is larger than the sum of its proper divisors (743674).

991556 is a wasteful number, since it uses less digits than its factorization.

991556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 247893 (or 247891 counting only the distinct ones).

The product of its digits is 12150, while the sum is 35.

The square root of 991556 is about 995.7690495291. The cubic root of 991556 is about 99.7177373610.

The spelling of 991556 in words is "nine hundred ninety-one thousand, five hundred fifty-six".