21778139438 has 16 divisors (see below), whose sum is σ = 35737922736. Its totient is φ = 9871107840.

The previous prime is 21778139401. The next prime is 21778139447. The reversal of 21778139438 is 83493187712.

It is a self number, because there is not a number n which added to its sum of digits gives 21778139438.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1394381 + ... + 1409912.

It is an arithmetic number, because the mean of its divisors is an integer number (2233620171).

Almost surely, 2^21778139438 is an apocalyptic number.

21778139438 is a deficient number, since it is larger than the sum of its proper divisors (13959783298).

21778139438 is a wasteful number, since it uses less digits than its factorization.

21778139438 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2804659.

The product of its digits is 2032128, while the sum is 53.

The spelling of 21778139438 in words is "twenty-one billion, seven hundred seventy-eight million, one hundred thirty-nine thousand, four hundred thirty-eight".