21700256 has 12 divisors (see below), whose sum is σ = 42722442. Its totient is φ = 10850112.

The previous prime is 21700253. The next prime is 21700291. The reversal of 21700256 is 65200712.

It can be written as a sum of positive squares in only one way, i.e., 16483600 + 5216656 = 4060^2 + 2284^2 .

It is a super-2 number, since 2×21700256² = 941802220931072, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21700253) 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 as a sum of consecutive naturals, namely, 339035 + ... + 339098.

Almost surely, 2^21700256 is an apocalyptic number.

It is an amenable number.

21700256 is a deficient number, since it is larger than the sum of its proper divisors (21022186).

21700256 is an equidigital number, since it uses as much as digits as its factorization.

21700256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 678143 (or 678135 counting only the distinct ones).

The product of its (nonzero) digits is 840, while the sum is 23.

The square root of 21700256 is about 4658.3533571424. The cubic root of 21700256 is about 278.9255420669.

Adding to 21700256 its reverse (65200712), we get a palindrome (86900968).

The spelling of 21700256 in words is "twenty-one million, seven hundred thousand, two hundred fifty-six".