261442631 has 4 divisors (see below), whose sum is σ = 261624264. Its totient is φ = 261261000.

The previous prime is 261442591. The next prime is 261442637. The reversal of 261442631 is 136244162.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261442631 is a prime.

It is a super-2 number, since 2×261442631² = 136704498608404322, 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 = 261442594 and 261442603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261442637) 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, 88640 + ... + 91541.

It is an arithmetic number, because the mean of its divisors is an integer number (65406066).

Almost surely, 2^261442631 is an apocalyptic number.

261442631 is a deficient number, since it is larger than the sum of its proper divisors (181633).

261442631 is a wasteful number, since it uses less digits than its factorization.

261442631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 181632.

The product of its digits is 6912, while the sum is 29.

The square root of 261442631 is about 16169.1877037778. The cubic root of 261442631 is about 639.4287146500.

Adding to 261442631 its reverse (136244162), we get a palindrome (397686793).

The spelling of 261442631 in words is "two hundred sixty-one million, four hundred forty-two thousand, six hundred thirty-one".