21245437 has 4 divisors (see below), whose sum is σ = 21819676. Its totient is φ = 20671200.

The previous prime is 21245417. The next prime is 21245459. The reversal of 21245437 is 73454212.

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

It can be written as a sum of positive squares in 2 ways, for example, as 14333796 + 6911641 = 3786^2 + 2629^2 .

It is a cyclic number.

It is not a de Polignac number, because 21245437 - 2⁷ = 21245309 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 (21245407) 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, 287064 + ... + 287137.

It is an arithmetic number, because the mean of its divisors is an integer number (5454919).

Almost surely, 2^21245437 is an apocalyptic number.

It is an amenable number.

21245437 is a deficient number, since it is larger than the sum of its proper divisors (574239).

21245437 is an equidigital number, since it uses as much as digits as its factorization.

21245437 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 574238.

The product of its digits is 6720, while the sum is 28.

The square root of 21245437 is about 4609.2772752352. The cubic root of 21245437 is about 276.9630859592.

Adding to 21245437 its reverse (73454212), we get a palindrome (94699649).

The spelling of 21245437 in words is "twenty-one million, two hundred forty-five thousand, four hundred thirty-seven".