21053517 has 4 divisors (see below), whose sum is σ = 28071360. Its totient is φ = 14035676.

The previous prime is 21053503. The next prime is 21053521. The reversal of 21053517 is 71535012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21053517 - 2¹⁵ = 21020749 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21053537) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3508917 + ... + 3508922.

It is an arithmetic number, because the mean of its divisors is an integer number (7017840).

Almost surely, 2^21053517 is an apocalyptic number.

It is an amenable number.

21053517 is a deficient number, since it is larger than the sum of its proper divisors (7017843).

21053517 is an equidigital number, since it uses as much as digits as its factorization.

21053517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7017842.

The product of its (nonzero) digits is 1050, while the sum is 24.

The square root of 21053517 is about 4588.4111629190. The cubic root of 21053517 is about 276.1265828727.

Adding to 21053517 its reverse (71535012), we get a palindrome (92588529).

The spelling of 21053517 in words is "twenty-one million, fifty-three thousand, five hundred seventeen".