1631891 has 4 divisors (see below), whose sum is σ = 1717800. Its totient is φ = 1545984.

The previous prime is 1631879. The next prime is 1631897. The reversal of 1631891 is 1981361.

It is a happy number.

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 1631891 - 2¹⁸ = 1369747 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1631897) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 42926 + ... + 42963.

It is an arithmetic number, because the mean of its divisors is an integer number (429450).

2^1631891 is an apocalyptic number.

1631891 is a deficient number, since it is larger than the sum of its proper divisors (85909).

1631891 is an equidigital number, since it uses as much as digits as its factorization.

1631891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 85908.

The product of its digits is 1296, while the sum is 29.

The square root of 1631891 is about 1277.4548915715. The cubic root of 1631891 is about 117.7326851297.

The spelling of 1631891 in words is "one million, six hundred thirty-one thousand, eight hundred ninety-one".