21245537 has 4 divisors (see below), whose sum is σ = 22169280. Its totient is φ = 20321796.

The previous prime is 21245533. The next prime is 21245557. The reversal of 21245537 is 73554212.

It is a happy number.

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 21245537 - 2² = 21245533 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21245531) 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, 461837 + ... + 461882.

It is an arithmetic number, because the mean of its divisors is an integer number (5542320).

Almost surely, 2^21245537 is an apocalyptic number.

It is an amenable number.

21245537 is a deficient number, since it is larger than the sum of its proper divisors (923743).

21245537 is an equidigital number, since it uses as much as digits as its factorization.

21245537 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 923742.

The product of its digits is 8400, while the sum is 29.

The square root of 21245537 is about 4609.2881229101. The cubic root of 21245537 is about 276.9635205037.

Adding to 21245537 its reverse (73554212), we get a palindrome (94799749).

The spelling of 21245537 in words is "twenty-one million, two hundred forty-five thousand, five hundred thirty-seven".