1664410781 has 12 divisors (see below), whose sum is σ = 1864001916. Its totient is φ = 1484545920.

The previous prime is 1664410771. The next prime is 1664410793. The reversal of 1664410781 is 1870144661.

It can be written as a sum of positive squares in 2 ways, for example, as 1140412900 + 523997881 = 33770^2 + 22891^2 .

It is not a de Polignac number, because 1664410781 - 2¹⁴ = 1664394397 is a prime.

It is a super-2 number, since 2×1664410781² = 5540526495818059922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1664410771) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 123356 + ... + 136181.

It is an arithmetic number, because the mean of its divisors is an integer number (155333493).

Almost surely, 2^1664410781 is an apocalyptic number.

1664410781 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1664410781 is a deficient number, since it is larger than the sum of its proper divisors (199591135).

1664410781 is a wasteful number, since it uses less digits than its factorization.

1664410781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 259612 (or 259601 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 38.

The square root of 1664410781 is about 40797.1908469198. The cubic root of 1664410781 is about 1185.0959303255.

The spelling of 1664410781 in words is "one billion, six hundred sixty-four million, four hundred ten thousand, seven hundred eighty-one".