21845690 has 16 divisors (see below), whose sum is σ = 39423240. Its totient is φ = 8715840.

The previous prime is 21845689. The next prime is 21845693. The reversal of 21845690 is 9654812.

It can be written as a sum of positive squares in 4 ways, for example, as 13476241 + 8369449 = 3671^2 + 2893^2 .

It is a super-2 number, since 2×21845690² = 954468343152200, which contains 22 as substring.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21845690.

It is not an unprimeable number, because it can be changed into a prime (21845693) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1616 + ... + 6804.

Almost surely, 2^21845690 is an apocalyptic number.

21845690 is a deficient number, since it is larger than the sum of its proper divisors (17577550).

21845690 is a wasteful number, since it uses less digits than its factorization.

21845690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5617.

The product of its (nonzero) digits is 17280, while the sum is 35.

The square root of 21845690 is about 4673.9373123738. The cubic root of 21845690 is about 279.5472700796.

The spelling of 21845690 in words is "twenty-one million, eight hundred forty-five thousand, six hundred ninety".