1664657620 has 12 divisors (see below), whose sum is σ = 3495781044. Its totient is φ = 665863040.

The previous prime is 1664657611. The next prime is 1664657633. The reversal of 1664657620 is 267564661.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 846926404 + 817731216 = 29102^2 + 28596^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 41616421 + ... + 41616460.

It is an arithmetic number, because the mean of its divisors is an integer number (291315087).

Almost surely, 2^1664657620 is an apocalyptic number.

1664657620 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1664657620 is an abundant number, since it is smaller than the sum of its proper divisors (1831123424).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1664657620 is a wasteful number, since it uses less digits than its factorization.

1664657620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83232890 (or 83232888 counting only the distinct ones).

The product of its (nonzero) digits is 362880, while the sum is 43.

The square root of 1664657620 is about 40800.2159308012. The cubic root of 1664657620 is about 1185.1545123049.

The spelling of 1664657620 in words is "one billion, six hundred sixty-four million, six hundred fifty-seven thousand, six hundred twenty".