561491921 has 2 divisors, whose sum is σ = 561491922. Its totient is φ = 561491920.

The previous prime is 561491899. The next prime is 561491951. The reversal of 561491921 is 129194165.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 558802321 + 2689600 = 23639^2 + 1640^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-561491921 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (561491951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 280745960 + 280745961.

It is an arithmetic number, because the mean of its divisors is an integer number (280745961).

Almost surely, 2^561491921 is an apocalyptic number.

It is an amenable number.

561491921 is a deficient number, since it is larger than the sum of its proper divisors (1).

561491921 is an equidigital number, since it uses as much as digits as its factorization.

561491921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 19440, while the sum is 38.

The square root of 561491921 is about 23695.8207496596. The cubic root of 561491921 is about 824.9883908988.

The spelling of 561491921 in words is "five hundred sixty-one million, four hundred ninety-one thousand, nine hundred twenty-one".