39911981 has 2 divisors, whose sum is σ = 39911982. Its totient is φ = 39911980.

The previous prime is 39911957. The next prime is 39911999. The reversal of 39911981 is 18911993.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 37319881 + 2592100 = 6109^2 + 1610^2 .

It is a cyclic number.

It is not a de Polignac number, because 39911981 - 2²² = 35717677 is a prime.

It is a super-2 number, since 2×39911981² = 3185932454688722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (39911941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 19955990 + 19955991.

It is an arithmetic number, because the mean of its divisors is an integer number (19955991).

Almost surely, 2^39911981 is an apocalyptic number.

It is an amenable number.

39911981 is a deficient number, since it is larger than the sum of its proper divisors (1).

39911981 is an equidigital number, since it uses as much as digits as its factorization.

39911981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17496, while the sum is 41.

The square root of 39911981 is about 6317.5929751765. The cubic root of 39911981 is about 341.7441544918.

The spelling of 39911981 in words is "thirty-nine million, nine hundred eleven thousand, nine hundred eighty-one".