21636737 has 4 divisors (see below), whose sum is σ = 21782100. Its totient is φ = 21491376.

The previous prime is 21636709. The next prime is 21636743. The reversal of 21636737 is 73763612.

It is a happy number.

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 10137856 + 11498881 = 3184^2 + 3391^2 .

It is a cyclic number.

It is not a de Polignac number, because 21636737 - 2¹² = 21632641 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21636697 and 21636706.

It is not an unprimeable number, because it can be changed into a prime (21636787) 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, 72458 + ... + 72755.

It is an arithmetic number, because the mean of its divisors is an integer number (5445525).

Almost surely, 2^21636737 is an apocalyptic number.

It is an amenable number.

21636737 is a deficient number, since it is larger than the sum of its proper divisors (145363).

21636737 is a wasteful number, since it uses less digits than its factorization.

21636737 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 145362.

The product of its digits is 31752, while the sum is 35.

The square root of 21636737 is about 4651.5306083052. The cubic root of 21636737 is about 278.6531276729.

The spelling of 21636737 in words is "twenty-one million, six hundred thirty-six thousand, seven hundred thirty-seven".