21470905 has 8 divisors (see below), whose sum is σ = 25796232. Its totient is φ = 17155968.

The previous prime is 21470903. The next prime is 21470909. The reversal of 21470905 is 50907412.

21470905 = 3276² + 3277².

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 6817321 + 14653584 = 2611^2 + 3828^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21470905 - 2¹ = 21470903 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21470903) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3087 + ... + 7243.

It is an arithmetic number, because the mean of its divisors is an integer number (3224529).

Almost surely, 2^21470905 is an apocalyptic number.

21470905 is the 3277-th centered square number.

It is an amenable number.

21470905 is a deficient number, since it is larger than the sum of its proper divisors (4325327).

21470905 is a wasteful number, since it uses less digits than its factorization.

21470905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5195.

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 21470905 is about 4633.6707910684. The cubic root of 21470905 is about 277.9394007278.

The spelling of 21470905 in words is "twenty-one million, four hundred seventy thousand, nine hundred five".