261637631 has 4 divisors (see below), whose sum is σ = 262680264. Its totient is φ = 260595000.

The previous prime is 261637609. The next prime is 261637637. The reversal of 261637631 is 136736162.

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 261637631 - 2⁶ = 261637567 is a prime.

It is a super-2 number, since 2×261637631² = 136908499910584322, 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 = 261637591 and 261637600.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261637637) 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, 520940 + ... + 521441.

It is an arithmetic number, because the mean of its divisors is an integer number (65670066).

Almost surely, 2^261637631 is an apocalyptic number.

261637631 is a deficient number, since it is larger than the sum of its proper divisors (1042633).

261637631 is a wasteful number, since it uses less digits than its factorization.

261637631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1042632.

The product of its digits is 27216, while the sum is 35.

The square root of 261637631 is about 16175.2165673292. The cubic root of 261637631 is about 639.5876502344.

The spelling of 261637631 in words is "two hundred sixty-one million, six hundred thirty-seven thousand, six hundred thirty-one".