21978914 has 8 divisors (see below), whose sum is σ = 33091740. Its totient is φ = 10948336.

The previous prime is 21978899. The next prime is 21978917. The reversal of 21978914 is 41987912.

It can be written as a sum of positive squares in 2 ways, for example, as 21780889 + 198025 = 4667^2 + 445^2 .

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 (21978917) 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, 19889 + ... + 20964.

Almost surely, 2^21978914 is an apocalyptic number.

21978914 is a deficient number, since it is larger than the sum of its proper divisors (11112826).

21978914 is a wasteful number, since it uses less digits than its factorization.

21978914 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41124.

The product of its digits is 36288, while the sum is 41.

The square root of 21978914 is about 4688.1674458150. The cubic root of 21978914 is about 280.1143835386.

It can be divided in two parts, 2197 and 8914, that added together give a palindrome (11111).

The spelling of 21978914 in words is "twenty-one million, nine hundred seventy-eight thousand, nine hundred fourteen".