261636517551 has 16 divisors (see below), whose sum is σ = 374137626240. Its totient is φ = 162126300960.

The previous prime is 261636517531. The next prime is 261636517567. The reversal of 261636517551 is 155715636162.

It is not a de Polignac number, because 261636517551 - 2¹⁵ = 261636484783 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 261636517551.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261636517531) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 43299945 + ... + 43305986.

It is an arithmetic number, because the mean of its divisors is an integer number (23383601640).

Almost surely, 2^261636517551 is an apocalyptic number.

261636517551 is a deficient number, since it is larger than the sum of its proper divisors (112501108689).

261636517551 is a wasteful number, since it uses less digits than its factorization.

261636517551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 86606006.

The product of its digits is 1134000, while the sum is 48.

The spelling of 261636517551 in words is "two hundred sixty-one billion, six hundred thirty-six million, five hundred seventeen thousand, five hundred fifty-one".