21787028778 has 32 divisors (see below), whose sum is σ = 44237827584. Its totient is φ = 7151780592.

The previous prime is 21787028773. The next prime is 21787028789. The reversal of 21787028778 is 87782078712.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21787028773) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1830001 + ... + 1841867.

It is an arithmetic number, because the mean of its divisors is an integer number (1382432112).

Almost surely, 2^21787028778 is an apocalyptic number.

21787028778 is an abundant number, since it is smaller than the sum of its proper divisors (22450798806).

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

21787028778 is a wasteful number, since it uses less digits than its factorization.

21787028778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16506.

The product of its (nonzero) digits is 4917248, while the sum is 57.

The spelling of 21787028778 in words is "twenty-one billion, seven hundred eighty-seven million, twenty-eight thousand, seven hundred seventy-eight".