21785169604 has 27 divisors (see below), whose sum is σ = 41911191021. Its totient is φ = 9900873840.

The previous prime is 21785169599. The next prime is 21785169607. The reversal of 21785169604 is 40696158712.

It is a happy number.

The square root of 21785169604 is 147598.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 14423529604 + 7361640000 = 120098^2 + 85800^2 .

It is a super-2 number, since 2×21785169604² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21785169607) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 3243802 + ... + 3250510.

Almost surely, 2^21785169604 is an apocalyptic number.

21785169604 is the 147598-th square number.

It is an amenable number.

21785169604 is a deficient number, since it is larger than the sum of its proper divisors (20126021417).

21785169604 is an frugal number, since it uses more digits than its factorization.

21785169604 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13444 (or 6722 counting only the distinct ones).

The product of its (nonzero) digits is 725760, while the sum is 49.

Multiplying 21785169604 by its sum of digits (49), we get a square (1067473310596 = 1033186²).

The spelling of 21785169604 in words is "twenty-one billion, seven hundred eighty-five million, one hundred sixty-nine thousand, six hundred four".