21545598961 has 2 divisors, whose sum is σ = 21545598962. Its totient is φ = 21545598960.

The previous prime is 21545598917. The next prime is 21545598983. The reversal of 21545598961 is 16989554512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16856088561 + 4689510400 = 129831^2 + 68480^2 .

It is a cyclic number.

It is not a de Polignac number, because 21545598961 - 2⁹ = 21545598449 is a prime.

It is not a weakly prime, because it can be changed into another prime (21545598161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10772799480 + 10772799481.

It is an arithmetic number, because the mean of its divisors is an integer number (10772799481).

Almost surely, 2^21545598961 is an apocalyptic number.

It is an amenable number.

21545598961 is a deficient number, since it is larger than the sum of its proper divisors (1).

21545598961 is an equidigital number, since it uses as much as digits as its factorization.

21545598961 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3888000, while the sum is 55.

The spelling of 21545598961 in words is "twenty-one billion, five hundred forty-five million, five hundred ninety-eight thousand, nine hundred sixty-one".