640465020621 has 6 divisors (see below), whose sum is σ = 925116140910. Its totient is φ = 426976680408.

The previous prime is 640465020617. The next prime is 640465020631. The reversal of 640465020621 is 126020564046.

640465020621 is a `hidden beast` number, since 6 + 4 + 0 + 4 + 6 + 5 + 0 + 20 + 621 = 666.

640465020621 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 331990306596 + 308474714025 = 576186^2 + 555405^2 .

It is not a de Polignac number, because 640465020621 - 2² = 640465020617 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640465020631) 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, 35581390026 + ... + 35581390043.

It is an arithmetic number, because the mean of its divisors is an integer number (154186023485).

Almost surely, 2^640465020621 is an apocalyptic number.

It is an amenable number.

640465020621 is a deficient number, since it is larger than the sum of its proper divisors (284651120289).

640465020621 is a wasteful number, since it uses less digits than its factorization.

640465020621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71162780075 (or 71162780072 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 36.

Adding to 640465020621 its reverse (126020564046), we get a palindrome (766485584667).

The spelling of 640465020621 in words is "six hundred forty billion, four hundred sixty-five million, twenty thousand, six hundred twenty-one".