21800917 has 2 divisors, whose sum is σ = 21800918. Its totient is φ = 21800916.

The previous prime is 21800897. The next prime is 21800921. The reversal of 21800917 is 71900812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19838116 + 1962801 = 4454^2 + 1401^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21800917 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21800017) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10900458 + 10900459.

It is an arithmetic number, because the mean of its divisors is an integer number (10900459).

Almost surely, 2^21800917 is an apocalyptic number.

It is an amenable number.

21800917 is a deficient number, since it is larger than the sum of its proper divisors (1).

21800917 is an equidigital number, since it uses as much as digits as its factorization.

21800917 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 21800917 is about 4669.1452108496. The cubic root of 21800917 is about 279.3561609813.

The spelling of 21800917 in words is "twenty-one million, eight hundred thousand, nine hundred seventeen".