15981981 has 4 divisors (see below), whose sum is σ = 21309312. Its totient is φ = 10654652.

The previous prime is 15981971. The next prime is 15982013. The reversal of 15981981 is 18918951.

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 a cyclic number.

It is not a de Polignac number, because 15981981 - 2⁵ = 15981949 is a prime.

It is a super-2 number, since 2×15981981² = 510847433368722, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15981971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2663661 + ... + 2663666.

It is an arithmetic number, because the mean of its divisors is an integer number (5327328).

Almost surely, 2^15981981 is an apocalyptic number.

It is an amenable number.

15981981 is a deficient number, since it is larger than the sum of its proper divisors (5327331).

15981981 is an equidigital number, since it uses as much as digits as its factorization.

15981981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5327330.

The product of its digits is 25920, while the sum is 42.

The square root of 15981981 is about 3997.7469904935. The cubic root of 15981981 is about 251.8895806241.

The spelling of 15981981 in words is "fifteen million, nine hundred eighty-one thousand, nine hundred eighty-one".