21636137 has 4 divisors (see below), whose sum is σ = 22044420. Its totient is φ = 21227856.

The previous prime is 21636107. The next prime is 21636143. The reversal of 21636137 is 73163612.

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 13957696 + 7678441 = 3736^2 + 2771^2 .

It is a cyclic number.

It is not a de Polignac number, because 21636137 - 2⁶ = 21636073 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21636107) 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, 204062 + ... + 204167.

It is an arithmetic number, because the mean of its divisors is an integer number (5511105).

Almost surely, 2^21636137 is an apocalyptic number.

It is an amenable number.

21636137 is a deficient number, since it is larger than the sum of its proper divisors (408283).

21636137 is an equidigital number, since it uses as much as digits as its factorization.

21636137 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 408282.

The product of its digits is 4536, while the sum is 29.

The square root of 21636137 is about 4651.4661129584. The cubic root of 21636137 is about 278.6505519083.

Adding to 21636137 its reverse (73163612), we get a palindrome (94799749).

The spelling of 21636137 in words is "twenty-one million, six hundred thirty-six thousand, one hundred thirty-seven".