21018380 has 24 divisors (see below), whose sum is σ = 44368800. Its totient is φ = 8363520.

The previous prime is 21018323. The next prime is 21018397. The reversal of 21018380 is 8381012.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1340 + ... + 6620.

It is an arithmetic number, because the mean of its divisors is an integer number (1848700).

Almost surely, 2^21018380 is an apocalyptic number.

21018380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21018380 is an abundant number, since it is smaller than the sum of its proper divisors (23350420).

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

21018380 is a wasteful number, since it uses less digits than its factorization.

21018380 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5489 (or 5487 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 23.

The square root of 21018380 is about 4584.5806787535. The cubic root of 21018380 is about 275.9728846848.

Adding to 21018380 its reverse (8381012), we get a palindrome (29399392).

The spelling of 21018380 in words is "twenty-one million, eighteen thousand, three hundred eighty".