21017240 has 16 divisors (see below), whose sum is σ = 47288880. Its totient is φ = 8406880.

The previous prime is 21017233. The next prime is 21017273. The reversal of 21017240 is 4271012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 262676 + ... + 262755.

It is an arithmetic number, because the mean of its divisors is an integer number (2955555).

Almost surely, 2^21017240 is an apocalyptic number.

21017240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21017240 is an abundant number, since it is smaller than the sum of its proper divisors (26271640).

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

21017240 is a wasteful number, since it uses less digits than its factorization.

21017240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 525442 (or 525438 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 17.

The square root of 21017240 is about 4584.4563472674. The cubic root of 21017240 is about 275.9678951664.

Adding to 21017240 its reverse (4271012), we get a palindrome (25288252).

The spelling of 21017240 in words is "twenty-one million, seventeen thousand, two hundred forty".