91721440667 has 4 divisors (see below), whose sum is σ = 93013292016. Its totient is φ = 90429589320.

The previous prime is 91721440631. The next prime is 91721440673. The reversal of 91721440667 is 76604412719.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-91721440667 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91721440627) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 645925568 + ... + 645925709.

It is an arithmetic number, because the mean of its divisors is an integer number (23253323004).

Almost surely, 2^91721440667 is an apocalyptic number.

91721440667 is a deficient number, since it is larger than the sum of its proper divisors (1291851349).

91721440667 is a wasteful number, since it uses less digits than its factorization.

91721440667 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1291851348.

The product of its (nonzero) digits is 508032, while the sum is 47.

The spelling of 91721440667 in words is "ninety-one billion, seven hundred twenty-one million, four hundred forty thousand, six hundred sixty-seven".