21978763 has 12 divisors (see below), whose sum is σ = 23454360. Its totient is φ = 20591136.

The previous prime is 21978743. The next prime is 21978779. The reversal of 21978763 is 36787912.

It is a happy number.

It is not a de Polignac number, because 21978763 - 2⁹ = 21978251 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21978743) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 38343 + ... + 38911.

It is an arithmetic number, because the mean of its divisors is an integer number (1954530).

Almost surely, 2^21978763 is an apocalyptic number.

21978763 is a deficient number, since it is larger than the sum of its proper divisors (1475597).

21978763 is a wasteful number, since it uses less digits than its factorization.

21978763 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 714 (or 695 counting only the distinct ones).

The product of its digits is 127008, while the sum is 43.

The square root of 21978763 is about 4688.1513414138. The cubic root of 21978763 is about 280.1137420546.

The spelling of 21978763 in words is "twenty-one million, nine hundred seventy-eight thousand, seven hundred sixty-three".