21503240 has 32 divisors (see below), whose sum is σ = 52781760. Its totient is φ = 7819200.

The previous prime is 21503227. The next prime is 21503263. The reversal of 21503240 is 4230512.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 23996 + ... + 24875.

It is an arithmetic number, because the mean of its divisors is an integer number (1649430).

Almost surely, 2^21503240 is an apocalyptic number.

21503240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21503240 is an abundant number, since it is smaller than the sum of its proper divisors (31278520).

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

21503240 is a wasteful number, since it uses less digits than its factorization.

21503240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48893 (or 48889 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 21503240 is about 4637.1586127714. The cubic root of 21503240 is about 278.0788555351.

Adding to 21503240 its reverse (4230512), we get a palindrome (25733752).

The spelling of 21503240 in words is "twenty-one million, five hundred three thousand, two hundred forty".