261236635501 has 6 divisors (see below), whose sum is σ = 273088581710. Its totient is φ = 249878520408.

The previous prime is 261236635493. The next prime is 261236635507. The reversal of 261236635501 is 105536632162.

It can be written as a sum of positive squares in only one way, i.e., 244871574025 + 16365061476 = 494845^2 + 127926^2 .

It is not a de Polignac number, because 261236635501 - 2³ = 261236635493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261236635507) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 246915006 + ... + 246916063.

Almost surely, 2^261236635501 is an apocalyptic number.

It is an amenable number.

261236635501 is a deficient number, since it is larger than the sum of its proper divisors (11851946209).

261236635501 is an equidigital number, since it uses as much as digits as its factorization.

261236635501 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 493831115 (or 493831092 counting only the distinct ones).

The product of its (nonzero) digits is 194400, while the sum is 40.

The spelling of 261236635501 in words is "two hundred sixty-one billion, two hundred thirty-six million, six hundred thirty-five thousand, five hundred one".