21785764 has 48 divisors (see below), whose sum is σ = 51198336. Its totient is φ = 7833600.

The previous prime is 21785749. The next prime is 21785767. The reversal of 21785764 is 46758712.

It is a zygodrome in base 3.

It is not an unprimeable number, because it can be changed into a prime (21785767) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1284 + ... + 6724.

It is an arithmetic number, because the mean of its divisors is an integer number (1066632).

Almost surely, 2^21785764 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 21785764, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25599168).

21785764 is an abundant number, since it is smaller than the sum of its proper divisors (29412572).

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

21785764 is a wasteful number, since it uses less digits than its factorization.

21785764 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5476 (or 5474 counting only the distinct ones).

The product of its digits is 94080, while the sum is 40.

The square root of 21785764 is about 4667.5222549014. The cubic root of 21785764 is about 279.2914226488.

It can be divided in two parts, 2178576 and 4, that multiplied together give a square (8714304 = 2952²).

The spelling of 21785764 in words is "twenty-one million, seven hundred eighty-five thousand, seven hundred sixty-four".