20816851637 has 4 divisors (see below), whose sum is σ = 20817470796. Its totient is φ = 20816232480.

The previous prime is 20816851631. The next prime is 20816851703. The reversal of 20816851637 is 73615861802.

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 17001812881 + 3815038756 = 130391^2 + 61766^2 .

It is a cyclic number.

It is not a de Polignac number, because 20816851637 - 2⁸ = 20816851381 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20816851591 and 20816851600.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20816851631) 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, 256064 + ... + 327417.

It is an arithmetic number, because the mean of its divisors is an integer number (5204367699).

Almost surely, 2^20816851637 is an apocalyptic number.

It is an amenable number.

20816851637 is a deficient number, since it is larger than the sum of its proper divisors (619159).

20816851637 is an equidigital number, since it uses as much as digits as its factorization.

20816851637 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 619158.

The product of its (nonzero) digits is 483840, while the sum is 47.

The spelling of 20816851637 in words is "twenty billion, eight hundred sixteen million, eight hundred fifty-one thousand, six hundred thirty-seven".