21573036637 has 4 divisors (see below), whose sum is σ = 21573539260. Its totient is φ = 21572534016.

The previous prime is 21573036623. The next prime is 21573036647. The reversal of 21573036637 is 73663037512.

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 10863684441 + 10709352196 = 104229^2 + 103486^2 .

It is a cyclic number.

It is not a de Polignac number, because 21573036637 - 2¹¹ = 21573034589 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21573036593 and 21573036602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21573036647) 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, 180228 + ... + 275005.

It is an arithmetic number, because the mean of its divisors is an integer number (5393384815).

Almost surely, 2^21573036637 is an apocalyptic number.

It is an amenable number.

21573036637 is a deficient number, since it is larger than the sum of its proper divisors (502623).

21573036637 is an equidigital number, since it uses as much as digits as its factorization.

21573036637 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 502622.

The product of its (nonzero) digits is 476280, while the sum is 43.

The spelling of 21573036637 in words is "twenty-one billion, five hundred seventy-three million, thirty-six thousand, six hundred thirty-seven".