20491778512 has 90 divisors (see below), whose sum is σ = 42680261778. Its totient is φ = 9529104384.

The previous prime is 20491778491. The next prime is 20491778519. The reversal of 20491778512 is 21587719402.

It can be written as a sum of positive squares in 9 ways, for example, as 328914496 + 20162864016 = 18136^2 + 141996^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20491778519) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 54937558 + ... + 54937930.

Almost surely, 2^20491778512 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20491778512, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21340130889).

20491778512 is an abundant number, since it is smaller than the sum of its proper divisors (22188483266).

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

20491778512 is a wasteful number, since it uses less digits than its factorization.

20491778512 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 633 (or 501 counting only the distinct ones).

The product of its (nonzero) digits is 282240, while the sum is 46.

The spelling of 20491778512 in words is "twenty billion, four hundred ninety-one million, seven hundred seventy-eight thousand, five hundred twelve".