21717090 has 48 divisors (see below), whose sum is σ = 56766528. Its totient is φ = 5760288.

The previous prime is 21717089. The next prime is 21717119. The reversal of 21717090 is 9071712.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 19899 + ... + 20961.

It is an arithmetic number, because the mean of its divisors is an integer number (1182636).

Almost surely, 2^21717090 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21717090, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28383264).

21717090 is an abundant number, since it is smaller than the sum of its proper divisors (35049438).

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

21717090 is a wasteful number, since it uses less digits than its factorization.

21717090 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1303 (or 1300 counting only the distinct ones).

The product of its (nonzero) digits is 882, while the sum is 27.

The square root of 21717090 is about 4660.1598685024. The cubic root of 21717090 is about 278.9976490340.

It can be divided in two parts, 2171 and 7090, that added together give a cube (9261 = 21³).

The spelling of 21717090 in words is "twenty-one million, seven hundred seventeen thousand, ninety".