139981 has 2 divisors, whose sum is σ = 139982. Its totient is φ = 139980.

The previous prime is 139969. The next prime is 139987. The reversal of 139981 is 189931.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 72900 + 67081 = 270^2 + 259^2 .

It is a cyclic number.

It is not a de Polignac number, because 139981 - 2¹¹ = 137933 is a prime.

It is a super-2 number, since 2×139981² = 39189360722, which contains 22 as substring.

It is an Ulam number.

It is a plaindrome in base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (139987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69990 + 69991.

It is an arithmetic number, because the mean of its divisors is an integer number (69991).

2¹³⁹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

139981 is a deficient number, since it is larger than the sum of its proper divisors (1).

139981 is an equidigital number, since it uses as much as digits as its factorization.

139981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1944, while the sum is 31.

The square root of 139981 is about 374.1403479979. The cubic root of 139981 is about 51.9225919268.

The spelling of 139981 in words is "one hundred thirty-nine thousand, nine hundred eighty-one".