21727978 has 8 divisors (see below), whose sum is σ = 32734980. Its totient is φ = 10816320.

The previous prime is 21727961. The next prime is 21727987. The reversal of 21727978 is 87972712.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 20857489 + 870489 = 4567^2 + 933^2 .

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

It is a plaindrome in base 13.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23263 + ... + 24178.

Almost surely, 2^21727978 is an apocalyptic number.

21727978 is a deficient number, since it is larger than the sum of its proper divisors (11007002).

21727978 is a wasteful number, since it uses less digits than its factorization.

21727978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47672.

The product of its digits is 98784, while the sum is 43.

The square root of 21727978 is about 4661.3279223843. The cubic root of 21727978 is about 279.0442669876.

The spelling of 21727978 in words is "twenty-one million, seven hundred twenty-seven thousand, nine hundred seventy-eight".