21978700 has 18 divisors (see below), whose sum is σ = 47693996. Its totient is φ = 8791440.

The previous prime is 21978673. The next prime is 21978701. The reversal of 21978700 is 787912.

It is not an unprimeable number, because it can be changed into a prime (21978701) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 109794 + ... + 109993.

Almost surely, 2^21978700 is an apocalyptic number.

21978700 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21978700 is an abundant number, since it is smaller than the sum of its proper divisors (25715296).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21978700 is a wasteful number, since it uses less digits than its factorization.

21978700 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 219801 (or 219794 counting only the distinct ones).

The product of its (nonzero) digits is 7056, while the sum is 34.

The square root of 21978700 is about 4688.1446223426. The cubic root of 21978700 is about 280.1134744147.

The spelling of 21978700 in words is "twenty-one million, nine hundred seventy-eight thousand, seven hundred".