16399538 has 4 divisors (see below), whose sum is σ = 24599310. Its totient is φ = 8199768.

The previous prime is 16399519. The next prime is 16399541. The reversal of 16399538 is 83599361.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 83599361 = 593 ⋅140977.

It can be written as a sum of positive squares in only one way, i.e., 12411529 + 3988009 = 3523^2 + 1997^2 .

It is a super-2 number, since 2×16399538² = 537889693226888, which contains 22 as substring.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4099883 + ... + 4099886.

Almost surely, 2^16399538 is an apocalyptic number.

16399538 is a deficient number, since it is larger than the sum of its proper divisors (8199772).

16399538 is an equidigital number, since it uses as much as digits as its factorization.

16399538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8199771.

The product of its digits is 174960, while the sum is 44.

The square root of 16399538 is about 4049.6343044774. The cubic root of 16399538 is about 254.0644327827.

The spelling of 16399538 in words is "sixteen million, three hundred ninety-nine thousand, five hundred thirty-eight".