21680226 has 48 divisors (see below), whose sum is σ = 49827960. Its totient is φ = 6800640.

The previous prime is 21680203. The next prime is 21680227. The reversal of 21680226 is 62208612.

It can be written as a sum of positive squares in 4 ways, for example, as 5688225 + 15992001 = 2385^2 + 3999^2 .

It is a super-2 number, since 2×21680226² = 940064398822152, 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 21680226.

It is not an unprimeable number, because it can be changed into a prime (21680227) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 20896 + ... + 21908.

Almost surely, 2^21680226 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21680226, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24913980).

21680226 is an abundant number, since it is smaller than the sum of its proper divisors (28147734).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21680226 is a wasteful number, since it uses less digits than its factorization.

21680226 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1091 (or 1088 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 27.

The square root of 21680226 is about 4656.2029594939. The cubic root of 21680226 is about 278.8396967134.

Adding to 21680226 its reverse (62208612), we get a palindrome (83888838).

The spelling of 21680226 in words is "twenty-one million, six hundred eighty thousand, two hundred twenty-six".