21351653 has 4 divisors (see below), whose sum is σ = 22040448. Its totient is φ = 20662860.

The previous prime is 21351637. The next prime is 21351661. The reversal of 21351653 is 35615312.

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 21351653 - 2⁴ = 21351637 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 (21351053) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 344351 + ... + 344412.

It is an arithmetic number, because the mean of its divisors is an integer number (5510112).

Almost surely, 2^21351653 is an apocalyptic number.

It is an amenable number.

21351653 is a deficient number, since it is larger than the sum of its proper divisors (688795).

21351653 is an equidigital number, since it uses as much as digits as its factorization.

21351653 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 688794.

The product of its digits is 2700, while the sum is 26.

The square root of 21351653 is about 4620.7848900376. The cubic root of 21351653 is about 277.4238754480.

Adding to 21351653 its reverse (35615312), we get a palindrome (56966965).

The spelling of 21351653 in words is "twenty-one million, three hundred fifty-one thousand, six hundred fifty-three".