21718628 has 6 divisors (see below), whose sum is σ = 38007606. Its totient is φ = 10859312.

The previous prime is 21718603. The next prime is 21718637. The reversal of 21718628 is 82681712.

It can be written as a sum of positive squares in only one way, i.e., 12730624 + 8988004 = 3568^2 + 2998^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2714825 + ... + 2714832.

It is an arithmetic number, because the mean of its divisors is an integer number (6334601).

Almost surely, 2^21718628 is an apocalyptic number.

It is an amenable number.

21718628 is a deficient number, since it is larger than the sum of its proper divisors (16288978).

21718628 is a wasteful number, since it uses less digits than its factorization.

21718628 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5429661 (or 5429659 counting only the distinct ones).

The product of its digits is 10752, while the sum is 35.

The square root of 21718628 is about 4660.3248813790. The cubic root of 21718628 is about 279.0042350646.

The spelling of 21718628 in words is "twenty-one million, seven hundred eighteen thousand, six hundred twenty-eight".