2181631 has 4 divisors (see below), whose sum is σ = 2240632. Its totient is φ = 2122632.

The previous prime is 2181629. The next prime is 2181649. The reversal of 2181631 is 1361812.

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 2181631 - 2¹ = 2181629 is a prime.

It is a super-2 number, since 2×2181631² = 9519027640322, 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 (2181601) 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 3 ways as a sum of consecutive naturals, for example, 29445 + ... + 29518.

It is an arithmetic number, because the mean of its divisors is an integer number (560158).

2^2181631 is an apocalyptic number.

2181631 is a deficient number, since it is larger than the sum of its proper divisors (59001).

2181631 is an equidigital number, since it uses as much as digits as its factorization.

2181631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59000.

The product of its digits is 288, while the sum is 22.

The square root of 2181631 is about 1477.0345290480. The cubic root of 2181631 is about 129.6961542877.

It can be divided in two parts, 218 and 1631, that added together give a square (1849 = 43²).

The spelling of 2181631 in words is "two million, one hundred eighty-one thousand, six hundred thirty-one".