21120019978 has 8 divisors (see below), whose sum is σ = 31680718272. Its totient is φ = 10559780556.

The previous prime is 21120019961. The next prime is 21120020029. The reversal of 21120019978 is 87991002112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21120019978² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21120019978.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 44601 + ... + 210307.

It is an arithmetic number, because the mean of its divisors is an integer number (3960089784).

Almost surely, 2^21120019978 is an apocalyptic number.

21120019978 is a deficient number, since it is larger than the sum of its proper divisors (10560698294).

21120019978 is a wasteful number, since it uses less digits than its factorization.

21120019978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 229436.

The product of its (nonzero) digits is 18144, while the sum is 40.

The spelling of 21120019978 in words is "twenty-one billion, one hundred twenty million, nineteen thousand, nine hundred seventy-eight".