991400961 has 4 divisors (see below), whose sum is σ = 1321867952. Its totient is φ = 660933972.

The previous prime is 991400957. The next prime is 991400999. The reversal of 991400961 is 169004199.

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.

It is not a de Polignac number, because 991400961 - 2² = 991400957 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (991400161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 165233491 + ... + 165233496.

It is an arithmetic number, because the mean of its divisors is an integer number (330466988).

Almost surely, 2^991400961 is an apocalyptic number.

It is an amenable number.

991400961 is a deficient number, since it is larger than the sum of its proper divisors (330466991).

991400961 is a wasteful number, since it uses less digits than its factorization.

991400961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 330466990.

The product of its (nonzero) digits is 17496, while the sum is 39.

The square root of 991400961 is about 31486.5203063152. The cubic root of 991400961 is about 997.1253982494.

The spelling of 991400961 in words is "nine hundred ninety-one million, four hundred thousand, nine hundred sixty-one".