21307380 has 48 divisors (see below), whose sum is σ = 59881920. Its totient is φ = 5660928.

The previous prime is 21307369. The next prime is 21307381. The reversal of 21307380 is 8370312.

It is a self number, because there is not a number n which added to its sum of digits gives 21307380.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21307381) 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, 22272 + ... + 23208.

It is an arithmetic number, because the mean of its divisors is an integer number (1247540).

Almost surely, 2^21307380 is an apocalyptic number.

21307380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21307380 is an abundant number, since it is smaller than the sum of its proper divisors (38574540).

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

21307380 is a wasteful number, since it uses less digits than its factorization.

21307380 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1328 (or 1326 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 24.

The square root of 21307380 is about 4615.9917677570. The cubic root of 21307380 is about 277.2319951242.

Adding to 21307380 its reverse (8370312), we get a palindrome (29677692).

The spelling of 21307380 in words is "twenty-one million, three hundred seven thousand, three hundred eighty".