1640925621 has 10 divisors (see below), whose sum is σ = 2451259382. Its totient is φ = 1093950360.

The previous prime is 1640925613. The next prime is 1640925661. The reversal of 1640925621 is 1265290461.

1640925621 is a `hidden beast` number, since 1 + 6 + 4 + 0 + 9 + 25 + 621 = 666.

It can be written as a sum of positive squares in only one way, i.e., 1245313521 + 395612100 = 35289^2 + 19890^2 .

It is not a de Polignac number, because 1640925621 - 2³ = 1640925613 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1640925661) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 10129090 + ... + 10129251.

Almost surely, 2^1640925621 is an apocalyptic number.

It is an amenable number.

1640925621 is a deficient number, since it is larger than the sum of its proper divisors (810333761).

1640925621 is an equidigital number, since it uses as much as digits as its factorization.

1640925621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20258353 (or 20258344 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 36.

The square root of 1640925621 is about 40508.3401412598. The cubic root of 1640925621 is about 1179.4955281594.

The spelling of 1640925621 in words is "one billion, six hundred forty million, nine hundred twenty-five thousand, six hundred twenty-one".