1664015 has 4 divisors (see below), whose sum is σ = 1996824. Its totient is φ = 1331208.

The previous prime is 1664009. The next prime is 1664017. The reversal of 1664015 is 5104661.

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

It is a cyclic number.

It is not a de Polignac number, because 1664015 - 2⁶ = 1663951 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1664017) 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, 166397 + ... + 166406.

It is an arithmetic number, because the mean of its divisors is an integer number (499206).

2^1664015 is an apocalyptic number.

1664015 is a deficient number, since it is larger than the sum of its proper divisors (332809).

1664015 is an equidigital number, since it uses as much as digits as its factorization.

1664015 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 332808.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 1664015 is about 1289.9670538428. The cubic root of 1664015 is about 118.5001988045.

Adding to 1664015 its reverse (5104661), we get a palindrome (6768676).

The spelling of 1664015 in words is "one million, six hundred sixty-four thousand, fifteen".