21065245 has 8 divisors (see below), whose sum is σ = 25625016. Its totient is φ = 16621056.

The previous prime is 21065207. The next prime is 21065273. The reversal of 21065245 is 54256012.

21065245 = 305² + 306² + ... + 450².

It can be written as a sum of positive squares in 4 ways, for example, as 1378276 + 19686969 = 1174^2 + 4437^2 .

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 21065245 - 2⁷ = 21065117 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28492 + ... + 29221.

It is an arithmetic number, because the mean of its divisors is an integer number (3203127).

Almost surely, 2^21065245 is an apocalyptic number.

It is an amenable number.

21065245 is a deficient number, since it is larger than the sum of its proper divisors (4559771).

21065245 is an equidigital number, since it uses as much as digits as its factorization.

21065245 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57791.

The product of its (nonzero) digits is 2400, while the sum is 25.

The square root of 21065245 is about 4589.6889872844. The cubic root of 21065245 is about 276.1778460643.

The spelling of 21065245 in words is "twenty-one million, sixty-five thousand, two hundred forty-five".