21745986978 has 16 divisors (see below), whose sum is σ = 44417335680. Its totient is φ = 7094435376.

The previous prime is 21745986971. The next prime is 21745987013. The reversal of 21745986978 is 87968954712.

It is not an unprimeable number, because it can be changed into a prime (21745986971) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 38556433 + ... + 38556996.

It is an arithmetic number, because the mean of its divisors is an integer number (2776083480).

Almost surely, 2^21745986978 is an apocalyptic number.

21745986978 is an abundant number, since it is smaller than the sum of its proper divisors (22671348702).

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

21745986978 is a wasteful number, since it uses less digits than its factorization.

21745986978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77113481.

The product of its digits is 60963840, while the sum is 66.

The spelling of 21745986978 in words is "twenty-one billion, seven hundred forty-five million, nine hundred eighty-six thousand, nine hundred seventy-eight".