21741664 has 72 divisors (see below), whose sum is σ = 51048144. Its totient is φ = 8928000.

The previous prime is 21741659. The next prime is 21741667. The reversal of 21741664 is 46614712.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21741667) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 215214 + ... + 215314.

It is an arithmetic number, because the mean of its divisors is an integer number (709002).

Almost surely, 2^21741664 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21741664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25524072).

21741664 is an abundant number, since it is smaller than the sum of its proper divisors (29306480).

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

21741664 is a wasteful number, since it uses less digits than its factorization.

21741664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 180 (or 141 counting only the distinct ones).

The product of its digits is 8064, while the sum is 31.

The square root of 21741664 is about 4662.7957278869. The cubic root of 21741664 is about 279.1028427447.

The spelling of 21741664 in words is "twenty-one million, seven hundred forty-one thousand, six hundred sixty-four".