91561921755 has 16 divisors (see below), whose sum is σ = 146640099840. Its totient is φ = 48786016608.

The previous prime is 91561921753. The next prime is 91561921757. The reversal of 91561921755 is 55712916519.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (91561921753) and next prime (91561921757).

It is not a de Polignac number, because 91561921755 - 2¹ = 91561921753 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 91561921698 and 91561921707.

It is not an unprimeable number, because it can be changed into a prime (91561921753) 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, 2921917 + ... + 2953086.

It is an arithmetic number, because the mean of its divisors is an integer number (9165006240).

Almost surely, 2^91561921755 is an apocalyptic number.

91561921755 is a deficient number, since it is larger than the sum of its proper divisors (55078178085).

91561921755 is a wasteful number, since it uses less digits than its factorization.

91561921755 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5876050.

The product of its digits is 850500, while the sum is 51.

The spelling of 91561921755 in words is "ninety-one billion, five hundred sixty-one million, nine hundred twenty-one thousand, seven hundred fifty-five".