21781510016678 has 4 divisors (see below), whose sum is σ = 32672265025020. Its totient is φ = 10890755008338.

The previous prime is 21781510016677. The next prime is 21781510016681. The reversal of 21781510016678 is 87661001518712.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21781510016677) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5445377504168 + ... + 5445377504171.

It is an arithmetic number, because the mean of its divisors is an integer number (8168066256255).

Almost surely, 2^{21781510016678} is an apocalyptic number.

21781510016678 is a deficient number, since it is larger than the sum of its proper divisors (10890755008342).

21781510016678 is a wasteful number, since it uses less digits than its factorization.

21781510016678 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10890755008341.

The product of its (nonzero) digits is 1128960, while the sum is 53.

The spelling of 21781510016678 in words is "twenty-one trillion, seven hundred eighty-one billion, five hundred ten million, sixteen thousand, six hundred seventy-eight".