21038517 has 6 divisors (see below), whose sum is σ = 30388982. Its totient is φ = 14025672.

The previous prime is 21038483. The next prime is 21038519. The reversal of 21038517 is 71583012.

It can be written as a sum of positive squares in only one way, i.e., 20439441 + 599076 = 4521^2 + 774^2 .

It is not a de Polignac number, because 21038517 - 2⁷ = 21038389 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21038519) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1168798 + ... + 1168815.

Almost surely, 2^21038517 is an apocalyptic number.

It is an amenable number.

21038517 is a deficient number, since it is larger than the sum of its proper divisors (9350465).

21038517 is a wasteful number, since it uses less digits than its factorization.

21038517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2337619 (or 2337616 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 27.

The square root of 21038517 is about 4586.7763189412. The cubic root of 21038517 is about 276.0609899872.

The spelling of 21038517 in words is "twenty-one million, thirty-eight thousand, five hundred seventeen".