20687312646 has 648 divisors, whose sum is σ = 65792405952. Its totient is φ = 4670265600.

The previous prime is 20687312617. The next prime is 20687312647. The reversal of 20687312646 is 64621378602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20687312647) by changing a digit.

It is a polite number, since it can be written in 323 ways as a sum of consecutive naturals, for example, 559116540 + ... + 559116576.

Almost surely, 2^20687312646 is an apocalyptic number.

20687312646 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 20687312646, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32896202976).

20687312646 is an abundant number, since it is smaller than the sum of its proper divisors (45105093306).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20687312646 is a wasteful number, since it uses less digits than its factorization.

20687312646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 138 (or 104 counting only the distinct ones).

The product of its (nonzero) digits is 580608, while the sum is 45.

It can be divided in two parts, 20687 and 312646, that added together give a palindrome (333333).

The spelling of 20687312646 in words is "twenty billion, six hundred eighty-seven million, three hundred twelve thousand, six hundred forty-six".