20687931890 has 32 divisors (see below), whose sum is σ = 39575427120. Its totient is φ = 7759427584.

The previous prime is 20687931863. The next prime is 20687931893. The reversal of 20687931890 is 9813978602.

It is a Cunningham number, because it is equal to 143833²+1.

It can be written as a sum of positive squares in 8 ways, for example, as 3331713841 + 17356218049 = 57721^2 + 131743^2 .

It is not an unprimeable number, because it can be changed into a prime (20687931893) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 180467 + ... + 271926.

Almost surely, 2^20687931890 is an apocalyptic number.

20687931890 is a deficient number, since it is larger than the sum of its proper divisors (18887495230).

20687931890 is a wasteful number, since it uses less digits than its factorization.

20687931890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 452686.

The product of its (nonzero) digits is 1306368, while the sum is 53.

The spelling of 20687931890 in words is "twenty billion, six hundred eighty-seven million, nine hundred thirty-one thousand, eight hundred ninety".