261956641489 has 9 divisors (see below), whose sum is σ = 264039156201. Its totient is φ = 259890436260.

The previous prime is 261956641469. The next prime is 261956641493. The reversal of 261956641489 is 984146659162.

It is a happy number.

The square root of 261956641489 is 511817.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 261956641489 - 2²¹ = 261954544337 is a prime.

It is a super-2 number, since 2×261956641489² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261956641469) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 67046074 + ... + 67049980.

Almost surely, 2^261956641489 is an apocalyptic number.

261956641489 is the 511817-th square number.

261956641489 is the 255909-th centered octagonal number.

It is an amenable number.

261956641489 is a deficient number, since it is larger than the sum of its proper divisors (2082514712).

261956641489 is an frugal number, since it uses more digits than its factorization.

261956641489 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8076 (or 4038 counting only the distinct ones).

The product of its digits is 22394880, while the sum is 61.

The spelling of 261956641489 in words is "two hundred sixty-one billion, nine hundred fifty-six million, six hundred forty-one thousand, four hundred eighty-nine".