21026917 has 2 divisors, whose sum is σ = 21026918. Its totient is φ = 21026916.

The previous prime is 21026911. The next prime is 21026933. The reversal of 21026917 is 71962012.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19660356 + 1366561 = 4434^2 + 1169^2 .

It is a cyclic number.

It is not a de Polignac number, because 21026917 - 2²³ = 12638309 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21026911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10513458 + 10513459.

It is an arithmetic number, because the mean of its divisors is an integer number (10513459).

Almost surely, 2^21026917 is an apocalyptic number.

It is an amenable number.

21026917 is a deficient number, since it is larger than the sum of its proper divisors (1).

21026917 is an equidigital number, since it uses as much as digits as its factorization.

21026917 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1512, while the sum is 28.

The square root of 21026917 is about 4585.5116399372. The cubic root of 21026917 is about 276.0102434411.

Adding to 21026917 its reverse (71962012), we get a palindrome (92988929).

The spelling of 21026917 in words is "twenty-one million, twenty-six thousand, nine hundred seventeen".