1631661 has 4 divisors (see below), whose sum is σ = 2175552. Its totient is φ = 1087772.

The previous prime is 1631659. The next prime is 1631683. The reversal of 1631661 is 1661361.

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.

It is a cyclic number.

It is not a de Polignac number, because 1631661 - 2¹ = 1631659 is a prime.

It is a D-number.

1631661 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1631611) 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, 271941 + ... + 271946.

It is an arithmetic number, because the mean of its divisors is an integer number (543888).

2^1631661 is an apocalyptic number.

It is an amenable number.

1631661 is a deficient number, since it is larger than the sum of its proper divisors (543891).

1631661 is an equidigital number, since it uses as much as digits as its factorization.

1631661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 543890.

The product of its digits is 648, while the sum is 24.

The square root of 1631661 is about 1277.3648656512. The cubic root of 1631661 is about 117.7271537575.

The spelling of 1631661 in words is "one million, six hundred thirty-one thousand, six hundred sixty-one".