21859645 has 8 divisors (see below), whose sum is σ = 26280504. Its totient is φ = 17455104.

The previous prime is 21859613. The next prime is 21859661. The reversal of 21859645 is 54695812.

It can be written as a sum of positive squares in 4 ways, for example, as 2172676 + 19686969 = 1474^2 + 4437^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21859645 - 2⁵ = 21859613 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21859598 and 21859607.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 904 + ... + 6673.

It is an arithmetic number, because the mean of its divisors is an integer number (3285063).

Almost surely, 2^21859645 is an apocalyptic number.

It is an amenable number.

21859645 is a deficient number, since it is larger than the sum of its proper divisors (4420859).

21859645 is an equidigital number, since it uses as much as digits as its factorization.

21859645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8159.

The product of its digits is 86400, while the sum is 40.

The square root of 21859645 is about 4675.4299267554. The cubic root of 21859645 is about 279.6067822271.

The spelling of 21859645 in words is "twenty-one million, eight hundred fifty-nine thousand, six hundred forty-five".