21919978 has 8 divisors (see below), whose sum is σ = 32902272. Its totient is φ = 10952556.

The previous prime is 21919957. The next prime is 21919979. The reversal of 21919978 is 87991912.

It is a happy number.

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

It is not an unprimeable number, because it can be changed into a prime (21919979) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1351 + ... + 6757.

It is an arithmetic number, because the mean of its divisors is an integer number (4112784).

Almost surely, 2^21919978 is an apocalyptic number.

21919978 is a deficient number, since it is larger than the sum of its proper divisors (10982294).

21919978 is a wasteful number, since it uses less digits than its factorization.

21919978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7436.

The product of its digits is 81648, while the sum is 46.

The square root of 21919978 is about 4681.8776148037. The cubic root of 21919978 is about 279.8637857862.

The spelling of 21919978 in words is "twenty-one million, nine hundred nineteen thousand, nine hundred seventy-eight".