21570240 has 56 divisors (see below), whose sum is σ = 68488560. Its totient is φ = 5751808.

The previous prime is 21570233. The next prime is 21570247. The reversal of 21570240 is 4207512.

It is an interprime number because it is at equal distance from previous prime (21570233) and next prime (21570247).

It is not an unprimeable number, because it can be changed into a prime (21570247) 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, 10275 + ... + 12194.

It is an arithmetic number, because the mean of its divisors is an integer number (1223010).

Almost surely, 2^21570240 is an apocalyptic number.

21570240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21570240 is an abundant number, since it is smaller than the sum of its proper divisors (46918320).

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

21570240 is a wasteful number, since it uses less digits than its factorization.

21570240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22489 (or 22479 counting only the distinct ones).

The product of its (nonzero) digits is 560, while the sum is 21.

The square root of 21570240 is about 4644.3772456595. The cubic root of 21570240 is about 278.3673696728.

Adding to 21570240 its reverse (4207512), we get a palindrome (25777752).

The spelling of 21570240 in words is "twenty-one million, five hundred seventy thousand, two hundred forty".