21978450 has 162 divisors, whose sum is σ = 67922829. Its totient is φ = 5091840.

The previous prime is 21978403. The next prime is 21978487. The reversal of 21978450 is 5487912.

It can be written as a sum of positive squares in 14 ways, for example, as 1212201 + 20766249 = 1101^2 + 4557^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=3315.

It is an unprimeable number.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 1292842 + ... + 1292858.

Almost surely, 2^21978450 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21978450

21978450 is an abundant number, since it is smaller than the sum of its proper divisors (45944379).

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

21978450 is a wasteful number, since it uses less digits than its factorization.

21978450 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78 (or 40 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The square root of 21978450 is about 4688.1179592668. The cubic root of 21978450 is about 280.1124123465.

The spelling of 21978450 in words is "twenty-one million, nine hundred seventy-eight thousand, four hundred fifty".