635661213331 has 4 divisors (see below), whose sum is σ = 637109189200. Its totient is φ = 634213237464.

The previous prime is 635661213329. The next prime is 635661213409. The reversal of 635661213331 is 133312166536.

It is a happy number.

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 635661213331 - 2¹ = 635661213329 is a prime.

It is a super-2 number, since 2×635661213331² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (635661211331) 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, 723987276 + ... + 723988153.

It is an arithmetic number, because the mean of its divisors is an integer number (159277297300).

Almost surely, 2^635661213331 is an apocalyptic number.

635661213331 is a deficient number, since it is larger than the sum of its proper divisors (1447975869).

635661213331 is a wasteful number, since it uses less digits than its factorization.

635661213331 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1447975868.

The product of its digits is 174960, while the sum is 40.

Adding to 635661213331 its reverse (133312166536), we get a palindrome (768973379867).

The spelling of 635661213331 in words is "six hundred thirty-five billion, six hundred sixty-one million, two hundred thirteen thousand, three hundred thirty-one".