91138027921 has 4 divisors (see below), whose sum is σ = 91139487012. Its totient is φ = 91136568832.

The previous prime is 91138027879. The next prime is 91138027927. The reversal of 91138027921 is 12972083119.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 34843822225 + 56294205696 = 186665^2 + 237264^2 .

It is a cyclic number.

It is not a de Polignac number, because 91138027921 - 2⁷ = 91138027793 is a prime.

It is a super-2 number, since 2×91138027921² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91138027927) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 631456 + ... + 762241.

It is an arithmetic number, because the mean of its divisors is an integer number (22784871753).

Almost surely, 2^91138027921 is an apocalyptic number.

It is an amenable number.

91138027921 is a deficient number, since it is larger than the sum of its proper divisors (1459091).

91138027921 is a wasteful number, since it uses less digits than its factorization.

91138027921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1459090.

The product of its (nonzero) digits is 54432, while the sum is 43.

The spelling of 91138027921 in words is "ninety-one billion, one hundred thirty-eight million, twenty-seven thousand, nine hundred twenty-one".