991991991901 has 8 divisors (see below), whose sum is σ = 1015191571680. Its totient is φ = 968798321232.

The previous prime is 991991991877. The next prime is 991991991923. The reversal of 991991991901 is 109199199199.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 991991991901 - 2¹⁷ = 991991860829 is a prime.

It is a super-2 number, since 2×991991991901² (a number of 25 digits) 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 (991991991701) 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, 1136695 + ... + 1809988.

It is an arithmetic number, because the mean of its divisors is an integer number (126898946460).

Almost surely, 2^991991991901 is an apocalyptic number.

It is an amenable number.

991991991901 is a deficient number, since it is larger than the sum of its proper divisors (23199579779).

991991991901 is a wasteful number, since it uses less digits than its factorization.

991991991901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2954555.

The product of its (nonzero) digits is 4782969, while the sum is 67.

The spelling of 991991991901 in words is "nine hundred ninety-one billion, nine hundred ninety-one million, nine hundred ninety-one thousand, nine hundred one".