1631981 has 8 divisors (see below), whose sum is σ = 1795584. Its totient is φ = 1473840.

The previous prime is 1631969. The next prime is 1631989. The reversal of 1631981 is 1891361.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1631981 is a prime.

It is a super-2 number, since 2×1631981² = 5326723968722, 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 (1631989) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 725 + ... + 1946.

It is an arithmetic number, because the mean of its divisors is an integer number (224448).

2^1631981 is an apocalyptic number.

It is an amenable number.

1631981 is a deficient number, since it is larger than the sum of its proper divisors (163603).

1631981 is a wasteful number, since it uses less digits than its factorization.

1631981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2731.

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

The square root of 1631981 is about 1277.4901173786. The cubic root of 1631981 is about 117.7348494383.

The spelling of 1631981 in words is "one million, six hundred thirty-one thousand, nine hundred eighty-one".