20687931689 has 2 divisors, whose sum is σ = 20687931690. Its totient is φ = 20687931688.

The previous prime is 20687931683. The next prime is 20687931697. The reversal of 20687931689 is 98613978602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15376000000 + 5311931689 = 124000^2 + 72883^2 .

It is a cyclic number.

It is not a de Polignac number, because 20687931689 - 2²⁴ = 20671154473 is a prime.

It is not a weakly prime, because it can be changed into another prime (20687931683) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10343965844 + 10343965845.

It is an arithmetic number, because the mean of its divisors is an integer number (10343965845).

Almost surely, 2^20687931689 is an apocalyptic number.

It is an amenable number.

20687931689 is a deficient number, since it is larger than the sum of its proper divisors (1).

20687931689 is an equidigital number, since it uses as much as digits as its factorization.

20687931689 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7838208, while the sum is 59.

The spelling of 20687931689 in words is "twenty billion, six hundred eighty-seven million, nine hundred thirty-one thousand, six hundred eighty-nine".