261663431 has 4 divisors (see below), whose sum is σ = 261934992. Its totient is φ = 261391872.

The previous prime is 261663397. The next prime is 261663481. The reversal of 261663431 is 134366162.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 261663431 - 2¹⁰ = 261662407 is a prime.

It is a super-2 number, since 2×261663431² = 136935502245383522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261663481) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 134330 + ... + 136263.

It is an arithmetic number, because the mean of its divisors is an integer number (65483748).

Almost surely, 2^261663431 is an apocalyptic number.

261663431 is a deficient number, since it is larger than the sum of its proper divisors (271561).

261663431 is an equidigital number, since it uses as much as digits as its factorization.

261663431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 271560.

The product of its digits is 15552, while the sum is 32.

The square root of 261663431 is about 16176.0140640394. The cubic root of 261663431 is about 639.6086727188.

The spelling of 261663431 in words is "two hundred sixty-one million, six hundred sixty-three thousand, four hundred thirty-one".