21024380 has 24 divisors (see below), whose sum is σ = 47548032. Its totient is φ = 7762752.

The previous prime is 21024379. The next prime is 21024389. The reversal of 21024380 is 8342012.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21024389) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40172 + ... + 40691.

It is an arithmetic number, because the mean of its divisors is an integer number (1981168).

Almost surely, 2^21024380 is an apocalyptic number.

21024380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21024380 is an abundant number, since it is smaller than the sum of its proper divisors (26523652).

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

21024380 is a wasteful number, since it uses less digits than its factorization.

21024380 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80885 (or 80883 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 20.

The square root of 21024380 is about 4585.2349994302. The cubic root of 21024380 is about 275.9991423344. Note that the first 3 decimals are identical.

Adding to 21024380 its reverse (8342012), we get a palindrome (29366392).

The spelling of 21024380 in words is "twenty-one million, twenty-four thousand, three hundred eighty".