21978350 has 12 divisors (see below), whose sum is σ = 40879824. Its totient is φ = 8791320.

The previous prime is 21978343. The next prime is 21978373. The reversal of 21978350 is 5387912.

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 21978350.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 219734 + ... + 219833.

It is an arithmetic number, because the mean of its divisors is an integer number (3406652).

Almost surely, 2^21978350 is an apocalyptic number.

21978350 is a deficient number, since it is larger than the sum of its proper divisors (18901474).

21978350 is a wasteful number, since it uses less digits than its factorization.

21978350 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 439579 (or 439574 counting only the distinct ones).

The product of its (nonzero) digits is 15120, while the sum is 35.

The square root of 21978350 is about 4688.1072939940. The cubic root of 21978350 is about 280.1119875169. Note that the first 3 decimals are identical.

The spelling of 21978350 in words is "twenty-one million, nine hundred seventy-eight thousand, three hundred fifty".