21226537 has 4 divisors (see below), whose sum is σ = 21911296. Its totient is φ = 20541780.

The previous prime is 21226531. The next prime is 21226547. The reversal of 21226537 is 73562212.

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 21226537 - 2⁷ = 21226409 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21226531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 342333 + ... + 342394.

It is an arithmetic number, because the mean of its divisors is an integer number (5477824).

Almost surely, 2^21226537 is an apocalyptic number.

It is an amenable number.

21226537 is a deficient number, since it is larger than the sum of its proper divisors (684759).

21226537 is an equidigital number, since it uses as much as digits as its factorization.

21226537 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 684758.

The product of its digits is 5040, while the sum is 28.

The square root of 21226537 is about 4607.2266061048. The cubic root of 21226537 is about 276.8809325485.

Adding to 21226537 its reverse (73562212), we get a palindrome (94788749).

The spelling of 21226537 in words is "twenty-one million, two hundred twenty-six thousand, five hundred thirty-seven".