91221973 has 2 divisors, whose sum is σ = 91221974. Its totient is φ = 91221972.

The previous prime is 91221967. The next prime is 91221989. The reversal of 91221973 is 37912219.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 76422564 + 14799409 = 8742^2 + 3847^2 .

It is a cyclic number.

It is not a de Polignac number, because 91221973 - 2⁹ = 91221461 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91221943) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45610986 + 45610987.

It is an arithmetic number, because the mean of its divisors is an integer number (45610987).

Almost surely, 2^91221973 is an apocalyptic number.

It is an amenable number.

91221973 is a deficient number, since it is larger than the sum of its proper divisors (1).

91221973 is an equidigital number, since it uses as much as digits as its factorization.

91221973 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6804, while the sum is 34.

The square root of 91221973 is about 9551.0194743807. The cubic root of 91221973 is about 450.1595697474.

The spelling of 91221973 in words is "ninety-one million, two hundred twenty-one thousand, nine hundred seventy-three".