21490345 has 4 divisors (see below), whose sum is σ = 25788420. Its totient is φ = 17192272.

The previous prime is 21490319. The next prime is 21490393. The reversal of 21490345 is 54309412.

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

It can be written as a sum of positive squares in 2 ways, for example, as 15280281 + 6210064 = 3909^2 + 2492^2 .

It is a cyclic number.

It is not a de Polignac number, because 21490345 - 2⁹ = 21489833 is a prime.

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

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2149030 + ... + 2149039.

It is an arithmetic number, because the mean of its divisors is an integer number (6447105).

Almost surely, 2^21490345 is an apocalyptic number.

It is an amenable number.

21490345 is a deficient number, since it is larger than the sum of its proper divisors (4298075).

21490345 is an equidigital number, since it uses as much as digits as its factorization.

21490345 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4298074.

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 21490345 is about 4635.7680054118. The cubic root of 21490345 is about 278.0232585823.

Adding to 21490345 its reverse (54309412), we get a palindrome (75799757).

The spelling of 21490345 in words is "twenty-one million, four hundred ninety thousand, three hundred forty-five".