1639997 has 4 divisors (see below), whose sum is σ = 1659840. Its totient is φ = 1620156.

The previous prime is 1639991. The next prime is 1639999. The reversal of 1639997 is 7999361.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 7999361 = 19 ⋅421019.

It is a cyclic number.

It is not a de Polignac number, because 1639997 - 2¹⁸ = 1377853 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1639991) 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, 9797 + ... + 9962.

It is an arithmetic number, because the mean of its divisors is an integer number (414960).

2^1639997 is an apocalyptic number.

It is an amenable number.

1639997 is a deficient number, since it is larger than the sum of its proper divisors (19843).

1639997 is an equidigital number, since it uses as much as digits as its factorization.

1639997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19842.

The product of its digits is 91854, while the sum is 44.

The square root of 1639997 is about 1280.6236761828. The cubic root of 1639997 is about 117.9272988924.

The spelling of 1639997 in words is "one million, six hundred thirty-nine thousand, nine hundred ninety-seven".