21023280 has 80 divisors (see below), whose sum is σ = 72420960. Its totient is φ = 5605632.

The previous prime is 21023279. The next prime is 21023287. The reversal of 21023280 is 8232012.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21023287) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2707 + ... + 7026.

It is an arithmetic number, because the mean of its divisors is an integer number (905262).

Almost surely, 2^21023280 is an apocalyptic number.

21023280 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21023280 is an abundant number, since it is smaller than the sum of its proper divisors (51397680).

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

21023280 is a wasteful number, since it uses less digits than its factorization.

21023280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9755 (or 9743 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

The square root of 21023280 is about 4585.1150476297. The cubic root of 21023280 is about 275.9943288060.

Adding to 21023280 its reverse (8232012), we get a palindrome (29255292).

The spelling of 21023280 in words is "twenty-one million, twenty-three thousand, two hundred eighty".