91106721 has 16 divisors (see below), whose sum is σ = 135121600. Its totient is φ = 60670944.

The previous prime is 91106713. The next prime is 91106753. The reversal of 91106721 is 12760119.

It is not a de Polignac number, because 91106721 - 2³ = 91106713 is a prime.

It is a super-2 number, since 2×91106721² = 16600869222743682, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91106761) 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, 41565 + ... + 43701.

It is an arithmetic number, because the mean of its divisors is an integer number (8445100).

Almost surely, 2^91106721 is an apocalyptic number.

It is an amenable number.

91106721 is a deficient number, since it is larger than the sum of its proper divisors (44014879).

91106721 is a wasteful number, since it uses less digits than its factorization.

91106721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3725 (or 3719 counting only the distinct ones).

The product of its (nonzero) digits is 756, while the sum is 27.

The square root of 91106721 is about 9544.9840754189. The cubic root of 91106721 is about 449.9699090990.

The spelling of 91106721 in words is "ninety-one million, one hundred six thousand, seven hundred twenty-one".