91947021 has 4 divisors (see below), whose sum is σ = 122596032. Its totient is φ = 61298012.

The previous prime is 91947017. The next prime is 91947041. The reversal of 91947021 is 12074919.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12074919 = 3 ⋅4024973.

It is a cyclic number.

It is not a de Polignac number, because 91947021 - 2² = 91947017 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91947001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15324501 + ... + 15324506.

It is an arithmetic number, because the mean of its divisors is an integer number (30649008).

Almost surely, 2^91947021 is an apocalyptic number.

It is an amenable number.

91947021 is a deficient number, since it is larger than the sum of its proper divisors (30649011).

91947021 is a wasteful number, since it uses less digits than its factorization.

91947021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30649010.

The product of its (nonzero) digits is 4536, while the sum is 33.

The square root of 91947021 is about 9588.9009276350. The cubic root of 91947021 is about 451.3490725090.

The spelling of 91947021 in words is "ninety-one million, nine hundred forty-seven thousand, twenty-one".