261907509361 has 9 divisors (see below), whose sum is σ = 262921128249. Its totient is φ = 260897789124.

The previous prime is 261907509341. The next prime is 261907509397. The reversal of 261907509361 is 163905709162.

The square root of 261907509361 is 511769.

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

It is not a de Polignac number, because 261907509361 - 2¹¹ = 261907507313 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261907509341) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 157112250 + ... + 157113916.

Almost surely, 2^261907509361 is an apocalyptic number.

261907509361 is the 511769-th square number.

261907509361 is the 255885-th centered octagonal number.

It is an amenable number.

261907509361 is a deficient number, since it is larger than the sum of its proper divisors (1013618888).

261907509361 is an frugal number, since it uses more digits than its factorization.

261907509361 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3948 (or 1974 counting only the distinct ones).

The product of its (nonzero) digits is 612360, while the sum is 49.

Multiplying 261907509361 by its sum of digits (49), we get a square (12833467958689 = 3582383²).

The spelling of 261907509361 in words is "two hundred sixty-one billion, nine hundred seven million, five hundred nine thousand, three hundred sixty-one".