991620440155751 has 8 divisors (see below), whose sum is σ = 1133294510535840. Its totient is φ = 849949871650848.

The previous prime is 991620440155747. The next prime is 991620440155759. The reversal of 991620440155751 is 157551044026199.

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 991620440155751 - 2² = 991620440155747 is a prime.

It is a super-2 number, since 2×991620440155751² (a number of 31 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 (991620440155759) 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, 874861976 + ... + 875994701.

It is an arithmetic number, because the mean of its divisors is an integer number (141661813816980).

Almost surely, 2^{991620440155751} is an apocalyptic number.

991620440155751 is a deficient number, since it is larger than the sum of its proper divisors (141674070380089).

991620440155751 is a wasteful number, since it uses less digits than its factorization.

991620440155751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1750937593.

The product of its (nonzero) digits is 13608000, while the sum is 59.

The spelling of 991620440155751 in words is "nine hundred ninety-one trillion, six hundred twenty billion, four hundred forty million, one hundred fifty-five thousand, seven hundred fifty-one".