261031631 has 4 divisors (see below), whose sum is σ = 298321872. Its totient is φ = 223741392.

The previous prime is 261031607. The next prime is 261031643. The reversal of 261031631 is 136130162.

It is a happy number.

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

It is not a de Polignac number, because 261031631 - 2²⁶ = 193922767 is a prime.

It is a super-2 number, since 2×261031631² = 136275024765040322, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 261031597 and 261031606.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261031601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18645110 + ... + 18645123.

It is an arithmetic number, because the mean of its divisors is an integer number (74580468).

Almost surely, 2^261031631 is an apocalyptic number.

261031631 is a deficient number, since it is larger than the sum of its proper divisors (37290241).

261031631 is an equidigital number, since it uses as much as digits as its factorization.

261031631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37290240.

The product of its (nonzero) digits is 648, while the sum is 23.

The square root of 261031631 is about 16156.4733466187. The cubic root of 261031631 is about 639.0934683347.

Adding to 261031631 its reverse (136130162), we get a palindrome (397161793).

The spelling of 261031631 in words is "two hundred sixty-one million, thirty-one thousand, six hundred thirty-one".