21689139 has 4 divisors (see below), whose sum is σ = 28918856. Its totient is φ = 14459424.

The previous prime is 21689131. The next prime is 21689149. The reversal of 21689139 is 93198612.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21689139 - 2³ = 21689131 is a prime.

It is a super-2 number, since 2×21689139² = 940837501122642, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21689097 and 21689106.

It is not an unprimeable number, because it can be changed into a prime (21689131) 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, 3614854 + ... + 3614859.

It is an arithmetic number, because the mean of its divisors is an integer number (7229714).

Almost surely, 2^21689139 is an apocalyptic number.

21689139 is a deficient number, since it is larger than the sum of its proper divisors (7229717).

21689139 is an equidigital number, since it uses as much as digits as its factorization.

21689139 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7229716.

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

The square root of 21689139 is about 4657.1599714848. The cubic root of 21689139 is about 278.8779029221.

The spelling of 21689139 in words is "twenty-one million, six hundred eighty-nine thousand, one hundred thirty-nine".