1966639 has 4 divisors (see below), whose sum is σ = 1970056. Its totient is φ = 1963224.

The previous prime is 1966619. The next prime is 1966663. The reversal of 1966639 is 9366691.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9366691 = 1613 ⋅5807.

It is a cyclic number.

It is not a de Polignac number, because 1966639 - 2⁵ = 1966607 is a prime.

It is a Duffinian number.

1966639 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1966619) 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, 609 + ... + 2074.

It is an arithmetic number, because the mean of its divisors is an integer number (492514).

2^1966639 is an apocalyptic number.

1966639 is a deficient number, since it is larger than the sum of its proper divisors (3417).

1966639 is an equidigital number, since it uses as much as digits as its factorization.

1966639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3416.

The product of its digits is 52488, while the sum is 40.

The square root of 1966639 is about 1402.3690669720. The cubic root of 1966639 is about 125.2876362819.

The spelling of 1966639 in words is "one million, nine hundred sixty-six thousand, six hundred thirty-nine".