91214561 has 2 divisors, whose sum is σ = 91214562. Its totient is φ = 91214560.

The previous prime is 91214551. The next prime is 91214597. The reversal of 91214561 is 16541219.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 88830625 + 2383936 = 9425^2 + 1544^2 .

It is an emirp because it is prime and its reverse (16541219) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 91214561 - 2²² = 87020257 is a prime.

It is a super-2 number, since 2×91214561² = 16640192276845442, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (91214521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45607280 + 45607281.

It is an arithmetic number, because the mean of its divisors is an integer number (45607281).

Almost surely, 2^91214561 is an apocalyptic number.

It is an amenable number.

91214561 is a deficient number, since it is larger than the sum of its proper divisors (1).

91214561 is an equidigital number, since it uses as much as digits as its factorization.

91214561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2160, while the sum is 29.

The square root of 91214561 is about 9550.6314450930. The cubic root of 91214561 is about 450.1473772424.

It can be divided in two parts, 9121 and 4561, that multiplied together give a triangular number (41600881 = T₉₁₂₁).

The spelling of 91214561 in words is "ninety-one million, two hundred fourteen thousand, five hundred sixty-one".