21106978 has 8 divisors (see below), whose sum is σ = 31951260. Its totient is φ = 10456560.

The previous prime is 21106961. The next prime is 21106993. The reversal of 21106978 is 87960112.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 16916769 + 4190209 = 4113^2 + 2047^2 .

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

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 48193 + ... + 48628.

Almost surely, 2^21106978 is an apocalyptic number.

21106978 is a deficient number, since it is larger than the sum of its proper divisors (10844282).

21106978 is a wasteful number, since it uses less digits than its factorization.

21106978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 96932.

The product of its (nonzero) digits is 6048, while the sum is 34.

The square root of 21106978 is about 4594.2331242548. The cubic root of 21106978 is about 276.3601072104.

The spelling of 21106978 in words is "twenty-one million, one hundred six thousand, nine hundred seventy-eight".