91061821 has 2 divisors, whose sum is σ = 91061822. Its totient is φ = 91061820.

The previous prime is 91061783. The next prime is 91061857. The reversal of 91061821 is 12816019.

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., 65448100 + 25613721 = 8090^2 + 5061^2 .

It is a cyclic number.

It is not a de Polignac number, because 91061821 - 2¹⁹ = 90537533 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 91061821.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91061881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45530910 + 45530911.

It is an arithmetic number, because the mean of its divisors is an integer number (45530911).

Almost surely, 2^91061821 is an apocalyptic number.

It is an amenable number.

91061821 is a deficient number, since it is larger than the sum of its proper divisors (1).

91061821 is an equidigital number, since it uses as much as digits as its factorization.

91061821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 864, while the sum is 28.

The square root of 91061821 is about 9542.6317648749. The cubic root of 91061821 is about 449.8959776020.

The spelling of 91061821 in words is "ninety-one million, sixty-one thousand, eight hundred twenty-one".