21078018 has 60 divisors (see below), whose sum is σ = 50681358. Its totient is φ = 6327360.

The previous prime is 21077971. The next prime is 21078053. The reversal of 21078018 is 81087012.

It can be written as a sum of positive squares in 5 ways, for example, as 8139609 + 12938409 = 2853^2 + 3597^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21077982 and 21078000.

It is an unprimeable number.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 514078 + ... + 514118.

Almost surely, 2^21078018 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21078018, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25340679).

21078018 is an abundant number, since it is smaller than the sum of its proper divisors (29603340).

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

21078018 is an equidigital number, since it uses as much as digits as its factorization.

21078018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101 (or 59 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 27.

The square root of 21078018 is about 4591.0802650357. The cubic root of 21078018 is about 276.2336553190.

The spelling of 21078018 in words is "twenty-one million, seventy-eight thousand, eighteen".