21290817 has 16 divisors (see below), whose sum is σ = 30205440. Its totient is φ = 13293312.

The previous prime is 21290813. The next prime is 21290839. The reversal of 21290817 is 71809212.

It is not a de Polignac number, because 21290817 - 2² = 21290813 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21290813) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10768 + ... + 12590.

It is an arithmetic number, because the mean of its divisors is an integer number (1887840).

Almost surely, 2^21290817 is an apocalyptic number.

It is an amenable number.

21290817 is a deficient number, since it is larger than the sum of its proper divisors (8914623).

21290817 is a wasteful number, since it uses less digits than its factorization.

21290817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2072.

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 21290817 is about 4614.1973299806. The cubic root of 21290817 is about 277.1601423383.

The spelling of 21290817 in words is "twenty-one million, two hundred ninety thousand, eight hundred seventeen".