1638981 has 8 divisors (see below), whose sum is σ = 2428160. Its totient is φ = 1092636.

The previous prime is 1638977. The next prime is 1638983. The reversal of 1638981 is 1898361.

It is not a de Polignac number, because 1638981 - 2² = 1638977 is a prime.

It is a super-2 number, since 2×1638981² = 5372517436722, which contains 22 as substring.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1638983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 30325 + ... + 30378.

It is an arithmetic number, because the mean of its divisors is an integer number (303520).

2^1638981 is an apocalyptic number.

It is an amenable number.

1638981 is a deficient number, since it is larger than the sum of its proper divisors (789179).

1638981 is an equidigital number, since it uses as much as digits as its factorization.

1638981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60712 (or 60706 counting only the distinct ones).

The product of its digits is 10368, while the sum is 36.

The square root of 1638981 is about 1280.2269330084. The cubic root of 1638981 is about 117.9029413506.

The spelling of 1638981 in words is "one million, six hundred thirty-eight thousand, nine hundred eighty-one".