21110978 has 16 divisors (see below), whose sum is σ = 36599040. Its totient is φ = 8945376.

The previous prime is 21110977. The next prime is 21110981. The reversal of 21110978 is 87901112.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21110978.

It is not an unprimeable number, because it can be changed into a prime (21110977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7226 + ... + 9717.

It is an arithmetic number, because the mean of its divisors is an integer number (2287440).

Almost surely, 2^21110978 is an apocalyptic number.

21110978 is a deficient number, since it is larger than the sum of its proper divisors (15488062).

21110978 is a wasteful number, since it uses less digits than its factorization.

21110978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17041.

The product of its (nonzero) digits is 1008, while the sum is 29.

The square root of 21110978 is about 4594.6684319981. The cubic root of 21110978 is about 276.3775638481.

The spelling of 21110978 in words is "twenty-one million, one hundred ten thousand, nine hundred seventy-eight".