991901901 has 16 divisors (see below), whose sum is σ = 1337656320. Its totient is φ = 653751360.

The previous prime is 991901899. The next prime is 991901951. The reversal of 991901901 is 109109199.

It is not a de Polignac number, because 991901901 - 2¹ = 991901899 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 991901901.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991901951) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 88660 + ... + 99218.

It is an arithmetic number, because the mean of its divisors is an integer number (83603520).

Almost surely, 2^991901901 is an apocalyptic number.

It is an amenable number.

991901901 is a deficient number, since it is larger than the sum of its proper divisors (345754419).

991901901 is a wasteful number, since it uses less digits than its factorization.

991901901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10916.

The product of its (nonzero) digits is 6561, while the sum is 39.

The square root of 991901901 is about 31494.4741343620. The cubic root of 991901901 is about 997.2933141281.

The spelling of 991901901 in words is "nine hundred ninety-one million, nine hundred one thousand, nine hundred one".