261821661706 has 24 divisors (see below), whose sum is σ = 457074186660. Its totient is φ = 112009265280.

The previous prime is 261821661701. The next prime is 261821661763. The reversal of 261821661706 is 607166128162.

It can be written as a sum of positive squares in 2 ways, for example, as 200189130625 + 61632531081 = 447425^2 + 248259^2 .

It is a super-2 number, since 2×261821661706² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (261821661701) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 31816701 + ... + 31824928.

Almost surely, 2^261821661706 is an apocalyptic number.

261821661706 is a deficient number, since it is larger than the sum of its proper divisors (195252524954).

261821661706 is a wasteful number, since it uses less digits than its factorization.

261821661706 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63641670 (or 63641659 counting only the distinct ones).

The product of its (nonzero) digits is 290304, while the sum is 46.

Adding to 261821661706 its reverse (607166128162), we get a palindrome (868987789868).

The spelling of 261821661706 in words is "two hundred sixty-one billion, eight hundred twenty-one million, six hundred sixty-one thousand, seven hundred six".