991900901 has 4 divisors (see below), whose sum is σ = 1001721804. Its totient is φ = 982080000.

The previous prime is 991900867. The next prime is 991900937. The reversal of 991900901 is 109009199.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 937951876 + 53949025 = 30626^2 + 7345^2 .

It is a cyclic number.

It is not a de Polignac number, because 991900901 - 2²² = 987706597 is a prime.

It is a super-2 number, since 2×991900901² = 1967734794809223602, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991900201) 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, 4910300 + ... + 4910501.

It is an arithmetic number, because the mean of its divisors is an integer number (250430451).

Almost surely, 2^991900901 is an apocalyptic number.

It is an amenable number.

991900901 is a deficient number, since it is larger than the sum of its proper divisors (9820903).

991900901 is a wasteful number, since it uses less digits than its factorization.

991900901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9820902.

The product of its (nonzero) digits is 6561, while the sum is 38.

The square root of 991900901 is about 31494.4582585572. The cubic root of 991900901 is about 997.2929789829.

The spelling of 991900901 in words is "nine hundred ninety-one million, nine hundred thousand, nine hundred one".