1664581 has 4 divisors (see below), whose sum is σ = 1681164. Its totient is φ = 1648000.

The previous prime is 1664569. The next prime is 1664627. The reversal of 1664581 is 1854661.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1221025 + 443556 = 1105^2 + 666^2 .

It is a cyclic number.

It is not a de Polignac number, because 1664581 - 2⁵ = 1664549 is a prime.

It is a super-2 number, since 2×1664581² = 5541659811122, 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 (1664501) 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, 8140 + ... + 8341.

It is an arithmetic number, because the mean of its divisors is an integer number (420291).

2^1664581 is an apocalyptic number.

It is an amenable number.

1664581 is a deficient number, since it is larger than the sum of its proper divisors (16583).

1664581 is a wasteful number, since it uses less digits than its factorization.

1664581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16582.

The product of its digits is 5760, while the sum is 31.

The square root of 1664581 is about 1290.1864206385. The cubic root of 1664581 is about 118.5136328800.

The spelling of 1664581 in words is "one million, six hundred sixty-four thousand, five hundred eighty-one".