640621623321 has 6 divisors (see below), whose sum is σ = 925342344810. Its totient is φ = 427081082208.

The previous prime is 640621623319. The next prime is 640621623329. The reversal of 640621623321 is 123326126046.

640621623321 is a `hidden beast` number, since 6 + 4 + 0 + 6 + 2 + 1 + 623 + 3 + 21 = 666.

It can be written as a sum of positive squares in only one way, i.e., 370559517696 + 270062105625 = 608736^2 + 519675^2 .

It is not a de Polignac number, because 640621623321 - 2¹ = 640621623319 is a prime.

It is a super-2 number, since 2×640621623321² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (640621623329) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35590090176 + ... + 35590090193.

It is an arithmetic number, because the mean of its divisors is an integer number (154223724135).

Almost surely, 2^640621623321 is an apocalyptic number.

It is an amenable number.

640621623321 is a deficient number, since it is larger than the sum of its proper divisors (284720721489).

640621623321 is a wasteful number, since it uses less digits than its factorization.

640621623321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71180180375 (or 71180180372 counting only the distinct ones).

The product of its (nonzero) digits is 62208, while the sum is 36.

Adding to 640621623321 its reverse (123326126046), we get a palindrome (763947749367).

The spelling of 640621623321 in words is "six hundred forty billion, six hundred twenty-one million, six hundred twenty-three thousand, three hundred twenty-one".