16399989 has 20 divisors (see below), whose sum is σ = 25566816. Its totient is φ = 10456776.

The previous prime is 16399987. The next prime is 16400017. The reversal of 16399989 is 98999361.

It is not a de Polignac number, because 16399989 - 2¹ = 16399987 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16399987) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 2539 + ... + 6264.

Almost surely, 2^16399989 is an apocalyptic number.

It is an amenable number.

16399989 is a deficient number, since it is larger than the sum of its proper divisors (9166827).

16399989 is an equidigital number, since it uses as much as digits as its factorization.

16399989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8838 (or 8829 counting only the distinct ones).

The product of its digits is 944784, while the sum is 54.

The square root of 16399989 is about 4049.6899881349. The cubic root of 16399989 is about 254.0667617509.

It can be divided in two parts, 1639 and 9989, that added together give a triangular number (11628 = T₁₅₂).

The spelling of 16399989 in words is "sixteen million, three hundred ninety-nine thousand, nine hundred eighty-nine".