15978881 has 2 divisors, whose sum is σ = 15978882. Its totient is φ = 15978880.

The previous prime is 15978871. The next prime is 15978883. The reversal of 15978881 is 18887951.

15978881 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12666481 + 3312400 = 3559^2 + 1820^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-15978881 is a prime.

It is a super-2 number, since 2×15978881² = 510649276024322, which contains 22 as substring.

Together with 15978883, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (15978883) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7989440 + 7989441.

It is an arithmetic number, because the mean of its divisors is an integer number (7989441).

Almost surely, 2^15978881 is an apocalyptic number.

It is an amenable number.

15978881 is a deficient number, since it is larger than the sum of its proper divisors (1).

15978881 is an equidigital number, since it uses as much as digits as its factorization.

15978881 is an evil number, because the sum of its binary digits is even.

The product of its digits is 161280, while the sum is 47.

The square root of 15978881 is about 3997.3592533071. The cubic root of 15978881 is about 251.8732933609.

The spelling of 15978881 in words is "fifteen million, nine hundred seventy-eight thousand, eight hundred eighty-one".