21162447978 has 24 divisors (see below), whose sum is σ = 48373464672. Its totient is φ = 6046144344.

The previous prime is 21162447923. The next prime is 21162447983. The reversal of 21162447978 is 87974426112.

It is a self number, because there is not a number n which added to its sum of digits gives 21162447978.

It is an unprimeable number.

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 11 ways as a sum of consecutive naturals, for example, 931551 + ... + 953997.

It is an arithmetic number, because the mean of its divisors is an integer number (2015561028).

Almost surely, 2^21162447978 is an apocalyptic number.

21162447978 is an abundant number, since it is smaller than the sum of its proper divisors (27211016694).

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

21162447978 is an frugal number, since it uses more digits than its factorization.

21162447978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44906 (or 22459 counting only the distinct ones).

The product of its digits is 1354752, while the sum is 51.

The spelling of 21162447978 in words is "twenty-one billion, one hundred sixty-two million, four hundred forty-seven thousand, nine hundred seventy-eight".