21389895 has 12 divisors (see below), whose sum is σ = 37075896. Its totient is φ = 11407920.

The previous prime is 21389891. The next prime is 21389903. The reversal of 21389895 is 59898312.

It is a happy number.

It is not a de Polignac number, because 21389895 - 2² = 21389891 is a prime.

It is a super-2 number, since 2×21389895² = 915055216222050, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45), and also a Moran number because the ratio is a prime number: 475331 = 21389895 / (2 + 1 + 3 + 8 + 9 + 8 + 9 + 5).

It is a self number, because there is not a number n which added to its sum of digits gives 21389895.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21389891) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 237621 + ... + 237710.

It is an arithmetic number, because the mean of its divisors is an integer number (3089658).

Almost surely, 2^21389895 is an apocalyptic number.

21389895 is a deficient number, since it is larger than the sum of its proper divisors (15686001).

21389895 is a wasteful number, since it uses less digits than its factorization.

21389895 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 475342 (or 475339 counting only the distinct ones).

The product of its digits is 155520, while the sum is 45.

The square root of 21389895 is about 4624.9210804078. The cubic root of 21389895 is about 277.5894038690.

The spelling of 21389895 in words is "twenty-one million, three hundred eighty-nine thousand, eight hundred ninety-five".