21297490 has 8 divisors (see below), whose sum is σ = 38335500. Its totient is φ = 8518992.

The previous prime is 21297487. The next prime is 21297509. The reversal of 21297490 is 9479212.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 21150801 + 146689 = 4599^2 + 383^2 .

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

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, 1064865 + ... + 1064884.

Almost surely, 2^21297490 is an apocalyptic number.

21297490 is a deficient number, since it is larger than the sum of its proper divisors (17038010).

21297490 is a wasteful number, since it uses less digits than its factorization.

21297490 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2129756.

The product of its (nonzero) digits is 9072, while the sum is 34.

The square root of 21297490 is about 4614.9203676770. The cubic root of 21297490 is about 277.1890952971.

The spelling of 21297490 in words is "twenty-one million, two hundred ninety-seven thousand, four hundred ninety".