261439291021 has 2 divisors, whose sum is σ = 261439291022. Its totient is φ = 261439291020.

The previous prime is 261439290997. The next prime is 261439291039. The reversal of 261439291021 is 120192934162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 205445534121 + 55993756900 = 453261^2 + 236630^2 .

It is a cyclic number.

It is not a de Polignac number, because 261439291021 - 2²¹ = 261437193869 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261439295021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130719645510 + 130719645511.

It is an arithmetic number, because the mean of its divisors is an integer number (130719645511).

Almost surely, 2^261439291021 is an apocalyptic number.

It is an amenable number.

261439291021 is a deficient number, since it is larger than the sum of its proper divisors (1).

261439291021 is an equidigital number, since it uses as much as digits as its factorization.

261439291021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 46656, while the sum is 40.

The spelling of 261439291021 in words is "two hundred sixty-one billion, four hundred thirty-nine million, two hundred ninety-one thousand, twenty-one".