20640681837 has 12 divisors (see below), whose sum is σ = 29908373820. Its totient is φ = 13717044288.

The previous prime is 20640681833. The next prime is 20640681839. The reversal of 20640681837 is 73818604602.

20640681837 is a `hidden beast` number, since 206 + 406 + 8 + 1 + 8 + 37 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 2368671561 + 18272010276 = 48669^2 + 135174^2 .

It is not a de Polignac number, because 20640681837 - 2² = 20640681833 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20640681792 and 20640681801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20640681833) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3614512 + ... + 3620217.

It is an arithmetic number, because the mean of its divisors is an integer number (2492364485).

Almost surely, 2^20640681837 is an apocalyptic number.

It is an amenable number.

20640681837 is a deficient number, since it is larger than the sum of its proper divisors (9267691983).

20640681837 is a wasteful number, since it uses less digits than its factorization.

20640681837 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7235052 (or 7235049 counting only the distinct ones).

The product of its (nonzero) digits is 387072, while the sum is 45.

The spelling of 20640681837 in words is "twenty billion, six hundred forty million, six hundred eighty-one thousand, eight hundred thirty-seven".