640621133531 has 4 divisors (see below), whose sum is σ = 640639265064. Its totient is φ = 640603002000.

The previous prime is 640621133491. The next prime is 640621133533. The reversal of 640621133531 is 135331126046.

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 640621133531 - 2²² = 640616939227 is a prime.

It is a super-2 number, since 2×640621133531² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 640621133491 and 640621133500.

It is not an unprimeable number, because it can be changed into a prime (640621133533) 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, 9012665 + ... + 9083466.

It is an arithmetic number, because the mean of its divisors is an integer number (160159816266).

Almost surely, 2^640621133531 is an apocalyptic number.

640621133531 is a deficient number, since it is larger than the sum of its proper divisors (18131533).

640621133531 is a wasteful number, since it uses less digits than its factorization.

640621133531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18131532.

The product of its (nonzero) digits is 38880, while the sum is 35.

Adding to 640621133531 its reverse (135331126046), we get a palindrome (775952259577).

The spelling of 640621133531 in words is "six hundred forty billion, six hundred twenty-one million, one hundred thirty-three thousand, five hundred thirty-one".