21042355678 has 4 divisors (see below), whose sum is σ = 31563533520. Its totient is φ = 10521177838.

The previous prime is 21042355661. The next prime is 21042355679. The reversal of 21042355678 is 87655324012.

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 (21042355679) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5260588918 + ... + 5260588921.

It is an arithmetic number, because the mean of its divisors is an integer number (7890883380).

Almost surely, 2^21042355678 is an apocalyptic number.

21042355678 is a deficient number, since it is larger than the sum of its proper divisors (10521177842).

21042355678 is a wasteful number, since it uses less digits than its factorization.

21042355678 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10521177841.

The product of its (nonzero) digits is 403200, while the sum is 43.

The spelling of 21042355678 in words is "twenty-one billion, forty-two million, three hundred fifty-five thousand, six hundred seventy-eight".