21050515 has 4 divisors (see below), whose sum is σ = 25260624. Its totient is φ = 16840408.

The previous prime is 21050509. The next prime is 21050527. The reversal of 21050515 is 51505012.

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

It is a cyclic number.

It is not a de Polignac number, because 21050515 - 2⁵ = 21050483 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21050492 and 21050501.

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, 2105047 + ... + 2105056.

It is an arithmetic number, because the mean of its divisors is an integer number (6315156).

Almost surely, 2^21050515 is an apocalyptic number.

21050515 is a deficient number, since it is larger than the sum of its proper divisors (4210109).

21050515 is an equidigital number, since it uses as much as digits as its factorization.

21050515 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4210108.

The product of its (nonzero) digits is 250, while the sum is 19.

The square root of 21050515 is about 4588.0840227703. The cubic root of 21050515 is about 276.1134580442.

Adding to 21050515 its reverse (51505012), we get a palindrome (72555527).

The spelling of 21050515 in words is "twenty-one million, fifty thousand, five hundred fifteen".