21781204578 has 48 divisors (see below), whose sum is σ = 54016213056. Its totient is φ = 6213762720.

The previous prime is 21781204573. The next prime is 21781204579. The reversal of 21781204578 is 87540218712.

21781204578 is a `hidden beast` number, since 2 + 1 + 78 + 1 + 2 + 0 + 4 + 578 = 666.

21781204578 is digitally balanced in base 5, because in such base it contains all the possibile digits an equal number of times.

It is not an unprimeable number, because it can be changed into a prime (21781204573) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 47476 + ... + 214047.

It is an arithmetic number, because the mean of its divisors is an integer number (1125337772).

Almost surely, 2^21781204578 is an apocalyptic number.

21781204578 is an abundant number, since it is smaller than the sum of its proper divisors (32235008478).

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

21781204578 is a wasteful number, since it uses less digits than its factorization.

21781204578 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 262199 (or 262196 counting only the distinct ones).

The product of its (nonzero) digits is 250880, while the sum is 45.

The spelling of 21781204578 in words is "twenty-one billion, seven hundred eighty-one million, two hundred four thousand, five hundred seventy-eight".