1381981 has 4 divisors (see below), whose sum is σ = 1463292. Its totient is φ = 1300672.

The previous prime is 1381979. The next prime is 1381993. The reversal of 1381981 is 1891831.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1891831 = 101 ⋅18731.

It can be written as a sum of positive squares in 2 ways, for example, as 632025 + 749956 = 795^2 + 866^2 .

It is a cyclic number.

It is not a de Polignac number, because 1381981 - 2¹ = 1381979 is a prime.

It is a super-2 number, since 2×1381981² = 3819742968722, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1381901) 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, 40630 + ... + 40663.

It is an arithmetic number, because the mean of its divisors is an integer number (365823).

2^1381981 is an apocalyptic number.

1381981 is the 744-th centered pentagonal number.

It is an amenable number.

1381981 is a deficient number, since it is larger than the sum of its proper divisors (81311).

1381981 is an equidigital number, since it uses as much as digits as its factorization.

1381981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81310.

The product of its digits is 1728, while the sum is 31.

The square root of 1381981 is about 1175.5768796638. The cubic root of 1381981 is about 111.3868760909.

The spelling of 1381981 in words is "one million, three hundred eighty-one thousand, nine hundred eighty-one".