21252643 has 4 divisors (see below), whose sum is σ = 21552048. Its totient is φ = 20953240.

The previous prime is 21252617. The next prime is 21252653. The reversal of 21252643 is 34625212.

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 21252643 - 2⁵ = 21252611 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21252653) 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, 149596 + ... + 149737.

It is an arithmetic number, because the mean of its divisors is an integer number (5388012).

Almost surely, 2^21252643 is an apocalyptic number.

21252643 is a deficient number, since it is larger than the sum of its proper divisors (299405).

21252643 is an equidigital number, since it uses as much as digits as its factorization.

21252643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 299404.

The product of its digits is 2880, while the sum is 25.

The square root of 21252643 is about 4610.0588933331. The cubic root of 21252643 is about 276.9943957474.

Adding to 21252643 its reverse (34625212), we get a palindrome (55877855).

The spelling of 21252643 in words is "twenty-one million, two hundred fifty-two thousand, six hundred forty-three".