1664287720 has 16 divisors (see below), whose sum is σ = 3744647460. Its totient is φ = 665715072.

The previous prime is 1664287711. The next prime is 1664287721. The reversal of 1664287720 is 277824661.

It can be written as a sum of positive squares in 2 ways, for example, as 1603041444 + 61246276 = 40038^2 + 7826^2 .

It is a super-2 number, since 2×1664287720² = 5539707229885596800, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1664287721) 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, 20803557 + ... + 20803636.

Almost surely, 2^1664287720 is an apocalyptic number.

1664287720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1664287720 is an abundant number, since it is smaller than the sum of its proper divisors (2080359740).

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

1664287720 is a wasteful number, since it uses less digits than its factorization.

1664287720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41607204 (or 41607200 counting only the distinct ones).

The product of its (nonzero) digits is 225792, while the sum is 43.

The square root of 1664287720 is about 40795.6826147081. The cubic root of 1664287720 is about 1185.0667222545.

The spelling of 1664287720 in words is "one billion, six hundred sixty-four million, two hundred eighty-seven thousand, seven hundred twenty".