9901561 has 2 divisors, whose sum is σ = 9901562. Its totient is φ = 9901560.

The previous prime is 9901553. The next prime is 9901571. The reversal of 9901561 is 1651099.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6661561 + 3240000 = 2581^2 + 1800^2 .

It is a cyclic number.

It is not a de Polignac number, because 9901561 - 2³ = 9901553 is a prime.

It is equal to p₆₅₈₅₄₃ and since 9901561 and 658543 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (9901571) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4950780 + 4950781.

It is an arithmetic number, because the mean of its divisors is an integer number (4950781).

Almost surely, 2^9901561 is an apocalyptic number.

It is an amenable number.

9901561 is a deficient number, since it is larger than the sum of its proper divisors (1).

9901561 is an equidigital number, since it uses as much as digits as its factorization.

9901561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2430, while the sum is 31.

The square root of 9901561 is about 3146.6745939166. The cubic root of 9901561 is about 214.7342019139.

The spelling of 9901561 in words is "nine million, nine hundred one thousand, five hundred sixty-one".