91438021 has 2 divisors, whose sum is σ = 91438022. Its totient is φ = 91438020.

The previous prime is 91438007. The next prime is 91438031. The reversal of 91438021 is 12083419.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 61308900 + 30129121 = 7830^2 + 5489^2 .

It is a cyclic number.

It is not a de Polignac number, because 91438021 - 2¹³ = 91429829 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91438031) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45719010 + 45719011.

It is an arithmetic number, because the mean of its divisors is an integer number (45719011).

Almost surely, 2^91438021 is an apocalyptic number.

It is an amenable number.

91438021 is a deficient number, since it is larger than the sum of its proper divisors (1).

91438021 is an equidigital number, since it uses as much as digits as its factorization.

91438021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 91438021 is about 9562.3229918258. The cubic root of 91438021 is about 450.5146720425.

The spelling of 91438021 in words is "ninety-one million, four hundred thirty-eight thousand, twenty-one".