261631605 has 8 divisors (see below), whose sum is σ = 418610592. Its totient is φ = 139536848.

The previous prime is 261631603. The next prime is 261631621. The reversal of 261631605 is 506136162.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 261631605 - 2¹ = 261631603 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261631603) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8721039 + ... + 8721068.

It is an arithmetic number, because the mean of its divisors is an integer number (52326324).

Almost surely, 2^261631605 is an apocalyptic number.

It is an amenable number.

261631605 is a deficient number, since it is larger than the sum of its proper divisors (156978987).

261631605 is a wasteful number, since it uses less digits than its factorization.

261631605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17442115.

The product of its (nonzero) digits is 6480, while the sum is 30.

The square root of 261631605 is about 16175.0302936347. The cubic root of 261631605 is about 639.5827399000.

Adding to 261631605 its reverse (506136162), we get a palindrome (767767767).

The spelling of 261631605 in words is "two hundred sixty-one million, six hundred thirty-one thousand, six hundred five".