1661639 has 6 divisors (see below), whose sum is σ = 1932984. Its totient is φ = 1424220.

The previous prime is 1661629. The next prime is 1661641. The reversal of 1661639 is 9361661.

It is not a de Polignac number, because 1661639 - 2⁴ = 1661623 is a prime.

It is a super-2 number, since 2×1661639² = 5522088332642, 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 (1661629) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 16907 + ... + 17004.

It is an arithmetic number, because the mean of its divisors is an integer number (322164).

2^1661639 is an apocalyptic number.

1661639 is a deficient number, since it is larger than the sum of its proper divisors (271345).

1661639 is an equidigital number, since it uses as much as digits as its factorization.

1661639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33925 (or 33918 counting only the distinct ones).

The product of its digits is 5832, while the sum is 32.

The square root of 1661639 is about 1289.0457711036. The cubic root of 1661639 is about 118.4437709102.

The spelling of 1661639 in words is "one million, six hundred sixty-one thousand, six hundred thirty-nine".