21242537 has 8 divisors (see below), whose sum is σ = 22874400. Its totient is φ = 19653184.

The previous prime is 21242527. The next prime is 21242539. The reversal of 21242537 is 73524212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21242537 - 2⁴ = 21242521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21242539) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9587 + ... + 11592.

It is an arithmetic number, because the mean of its divisors is an integer number (2859300).

Almost surely, 2^21242537 is an apocalyptic number.

It is an amenable number.

21242537 is a deficient number, since it is larger than the sum of its proper divisors (1631863).

21242537 is a wasteful number, since it uses less digits than its factorization.

21242537 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21255.

The product of its digits is 3360, while the sum is 26.

The square root of 21242537 is about 4608.9626815586. The cubic root of 21242537 is about 276.9504835747.

Adding to 21242537 its reverse (73524212), we get a palindrome (94766749).

The spelling of 21242537 in words is "twenty-one million, two hundred forty-two thousand, five hundred thirty-seven".