16921389 has 4 divisors (see below), whose sum is σ = 22561856. Its totient is φ = 11280924.

The previous prime is 16921379. The next prime is 16921391. The reversal of 16921389 is 98312961.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 16921389 - 2⁵ = 16921357 is a prime.

It is a super-4 number, since 4×16921389⁴ (a number of 30 digits) contains 4444 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16921309) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2820229 + ... + 2820234.

It is an arithmetic number, because the mean of its divisors is an integer number (5640464).

Almost surely, 2^16921389 is an apocalyptic number.

It is an amenable number.

16921389 is a deficient number, since it is larger than the sum of its proper divisors (5640467).

16921389 is an equidigital number, since it uses as much as digits as its factorization.

16921389 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5640466.

The product of its digits is 23328, while the sum is 39.

The square root of 16921389 is about 4113.5615955033. The cubic root of 16921389 is about 256.7312112557.

It can be divided in two parts, 1692 and 1389, that added together give a triangular number (3081 = T₇₈).

The spelling of 16921389 in words is "sixteen million, nine hundred twenty-one thousand, three hundred eighty-nine".