20921640678 has 12 divisors (see below), whose sum is σ = 45330221508. Its totient is φ = 6973880220.

The previous prime is 20921640671. The next prime is 20921640683. The reversal of 20921640678 is 87604612902.

It is a happy number.

20921640678 is a `hidden beast` number, since 20 + 9 + 216 + 406 + 7 + 8 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20921640671) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 581156668 + ... + 581156703.

It is an arithmetic number, because the mean of its divisors is an integer number (3777518459).

Almost surely, 2^20921640678 is an apocalyptic number.

20921640678 is an abundant number, since it is smaller than the sum of its proper divisors (24408580830).

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

20921640678 is a wasteful number, since it uses less digits than its factorization.

20921640678 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1162313379 (or 1162313376 counting only the distinct ones).

The product of its (nonzero) digits is 290304, while the sum is 45.

The spelling of 20921640678 in words is "twenty billion, nine hundred twenty-one million, six hundred forty thousand, six hundred seventy-eight".