21717487 has 16 divisors (see below), whose sum is σ = 24393600. Its totient is φ = 19167840.

The previous prime is 21717473. The next prime is 21717523. The reversal of 21717487 is 78471712.

It is a cyclic number.

It is not a de Polignac number, because 21717487 - 2²³ = 13328879 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21717407) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 70588 + ... + 70894.

It is an arithmetic number, because the mean of its divisors is an integer number (1524600).

Almost surely, 2^21717487 is an apocalyptic number.

21717487 is a deficient number, since it is larger than the sum of its proper divisors (2676113).

21717487 is a wasteful number, since it uses less digits than its factorization.

21717487 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 486.

The product of its digits is 21952, while the sum is 37.

The square root of 21717487 is about 4660.2024634129. The cubic root of 21717487 is about 278.9993490990. Note that the first 3 decimals are identical.

The spelling of 21717487 in words is "twenty-one million, seven hundred seventeen thousand, four hundred eighty-seven".