21570380 has 24 divisors (see below), whose sum is σ = 48782832. Its totient is φ = 7964352.

The previous prime is 21570379. The next prime is 21570383. The reversal of 21570380 is 8307512.

It is a Harshad number since it is a multiple of its sum of digits (26).

It is not an unprimeable number, because it can be changed into a prime (21570383) 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, 41222 + ... + 41741.

It is an arithmetic number, because the mean of its divisors is an integer number (2032618).

Almost surely, 2^21570380 is an apocalyptic number.

21570380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21570380 is an abundant number, since it is smaller than the sum of its proper divisors (27212452).

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

21570380 is a wasteful number, since it uses less digits than its factorization.

21570380 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82985 (or 82983 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 26.

The square root of 21570380 is about 4644.3923176235. The cubic root of 21570380 is about 278.3679719123.

Adding to 21570380 its reverse (8307512), we get a palindrome (29877892).

The spelling of 21570380 in words is "twenty-one million, five hundred seventy thousand, three hundred eighty".