15999989 has 2 divisors, whose sum is σ = 15999990. Its totient is φ = 15999988.

The previous prime is 15999983. The next prime is 16000057. The reversal of 15999989 is 98999951.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9972964 + 6027025 = 3158^2 + 2455^2 .

It is a cyclic number.

It is not a de Polignac number, because 15999989 - 2¹⁶ = 15934453 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15999983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7999994 + 7999995.

It is an arithmetic number, because the mean of its divisors is an integer number (7999995).

Almost surely, 2^15999989 is an apocalyptic number.

It is an amenable number.

15999989 is a deficient number, since it is larger than the sum of its proper divisors (1).

15999989 is an equidigital number, since it uses as much as digits as its factorization.

15999989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2361960, while the sum is 59.

The square root of 15999989 is about 3999.9986249998. The cubic root of 15999989 is about 251.9841522326.

The spelling of 15999989 in words is "fifteen million, nine hundred ninety-nine thousand, nine hundred eighty-nine".