21856745 has 12 divisors (see below), whose sum is σ = 27683460. Its totient is φ = 16563744.

The previous prime is 21856741. The next prime is 21856759. The reversal of 21856745 is 54765812.

It can be written as a sum of positive squares in 2 ways, for example, as 16999129 + 4857616 = 4123^2 + 2204^2 .

It is not a de Polignac number, because 21856745 - 2² = 21856741 is a prime.

It is a Smith number, since the sum of its digits (38) coincides with the sum of the digits of its prime factors.

It is an alternating number because its digits alternate between even and odd.

It is a junction number, because it is equal to n+sod(n) for n = 21856699 and 21856708.

It is not an unprimeable number, because it can be changed into a prime (21856741) 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, 4250 + ... + 7859.

It is an arithmetic number, because the mean of its divisors is an integer number (2306955).

Almost surely, 2^21856745 is an apocalyptic number.

It is an amenable number.

21856745 is a deficient number, since it is larger than the sum of its proper divisors (5826715).

21856745 is a wasteful number, since it uses less digits than its factorization.

21856745 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12152 (or 12133 counting only the distinct ones).

The product of its digits is 67200, while the sum is 38.

The square root of 21856745 is about 4675.1197845617. The cubic root of 21856745 is about 279.5944170442.

The spelling of 21856745 in words is "twenty-one million, eight hundred fifty-six thousand, seven hundred forty-five".