991917940 has 24 divisors (see below), whose sum is σ = 2243261160. Its totient is φ = 366246528.

The previous prime is 991917931. The next prime is 991917947. The reversal of 991917940 is 49719199.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 675684 + 991242256 = 822^2 + 31484^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991917947) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1907275 + ... + 1907794.

It is an arithmetic number, because the mean of its divisors is an integer number (93469215).

Almost surely, 2^991917940 is an apocalyptic number.

It is an amenable number.

991917940 is an abundant number, since it is smaller than the sum of its proper divisors (1251343220).

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

991917940 is a wasteful number, since it uses less digits than its factorization.

991917940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3815091 (or 3815089 counting only the distinct ones).

The product of its (nonzero) digits is 183708, while the sum is 49.

The square root of 991917940 is about 31494.7287653029. The cubic root of 991917940 is about 997.2986894921.

The spelling of 991917940 in words is "nine hundred ninety-one million, nine hundred seventeen thousand, nine hundred forty".