21717428 has 24 divisors (see below), whose sum is σ = 40340160. Its totient is φ = 10208000.

The previous prime is 21717407. The next prime is 21717461. The reversal of 21717428 is 82471712.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21717394 and 21717403.

It is a congruent number.

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, 3428 + ... + 7428.

It is an arithmetic number, because the mean of its divisors is an integer number (1680840).

Almost surely, 2^21717428 is an apocalyptic number.

It is an amenable number.

21717428 is a deficient number, since it is larger than the sum of its proper divisors (18622732).

21717428 is a wasteful number, since it uses less digits than its factorization.

21717428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4087 (or 4085 counting only the distinct ones).

The product of its digits is 6272, while the sum is 32.

The square root of 21717428 is about 4660.1961332116. The cubic root of 21717428 is about 278.9990964458. Note that the first 3 decimals are identical.

The spelling of 21717428 in words is "twenty-one million, seven hundred seventeen thousand, four hundred twenty-eight".