15681989 has 2 divisors, whose sum is σ = 15681990. Its totient is φ = 15681988.

The previous prime is 15681947. The next prime is 15681997. The reversal of 15681989 is 98918651.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15249025 + 432964 = 3905^2 + 658^2 .

It is a cyclic number.

It is not a de Polignac number, because 15681989 - 2⁸ = 15681733 is a prime.

It is a super-2 number, since 2×15681989² = 491849557992242, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15681389) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7840994 + 7840995.

It is an arithmetic number, because the mean of its divisors is an integer number (7840995).

Almost surely, 2^15681989 is an apocalyptic number.

It is an amenable number.

15681989 is a deficient number, since it is larger than the sum of its proper divisors (1).

15681989 is an equidigital number, since it uses as much as digits as its factorization.

15681989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 155520, while the sum is 47.

The square root of 15681989 is about 3960.0491158570. The cubic root of 15681989 is about 250.3035725589.

The spelling of 15681989 in words is "fifteen million, six hundred eighty-one thousand, nine hundred eighty-nine".