39981 has 4 divisors (see below), whose sum is σ = 53312. Its totient is φ = 26652.

The previous prime is 39979. The next prime is 39983. The reversal of 39981 is 18993.

It is a happy number.

39981 is digitally balanced in base 2 and base 4, because in such bases it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (39979) and next prime (39983).

It is not a de Polignac number, because 39981 - 2¹ = 39979 is a prime.

It is a super-2 number, since 2×39981² = 3196960722, which contains 22 as substring.

It is an Ulam number.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 39981.

It is not an unprimeable number, because it can be changed into a prime (39983) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6661 + ... + 6666.

It is an arithmetic number, because the mean of its divisors is an integer number (13328).

2³⁹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

39981 is a deficient number, since it is larger than the sum of its proper divisors (13331).

39981 is a wasteful number, since it uses less digits than its factorization.

39981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13330.

The product of its digits is 1944, while the sum is 30.

The square root of 39981 is about 199.9524943580. The cubic root of 39981 is about 34.1941031521.

The spelling of 39981 in words is "thirty-nine thousand, nine hundred eighty-one".