21717040 has 20 divisors (see below), whose sum is σ = 50492304. Its totient is φ = 8686784.

The previous prime is 21717029. The next prime is 21717043. The reversal of 21717040 is 4071712.

It is a tau number, because it is divible by the number of its divisors (20).

It is not an unprimeable number, because it can be changed into a prime (21717043) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 135652 + ... + 135811.

Almost surely, 2^21717040 is an apocalyptic number.

21717040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21717040 is an abundant number, since it is smaller than the sum of its proper divisors (28775264).

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

21717040 is a wasteful number, since it uses less digits than its factorization.

21717040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 271476 (or 271470 counting only the distinct ones).

The product of its (nonzero) digits is 392, while the sum is 22.

The square root of 21717040 is about 4660.1545038765. The cubic root of 21717040 is about 278.9974349186.

Adding to 21717040 its reverse (4071712), we get a palindrome (25788752).

The spelling of 21717040 in words is "twenty-one million, seven hundred seventeen thousand, forty".