21726121 has 2 divisors, whose sum is σ = 21726122. Its totient is φ = 21726120.

The previous prime is 21726113. The next prime is 21726143. The reversal of 21726121 is 12162712.

It is a happy number.

It is an a-pointer prime, because the next prime (21726143) can be obtained adding 21726121 to its sum of digits (22).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20602521 + 1123600 = 4539^2 + 1060^2 .

It is a cyclic number.

It is not a de Polignac number, because 21726121 - 2³ = 21726113 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21726092 and 21726101.

It is not a weakly prime, because it can be changed into another prime (21726151) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10863060 + 10863061.

It is an arithmetic number, because the mean of its divisors is an integer number (10863061).

Almost surely, 2^21726121 is an apocalyptic number.

It is an amenable number.

21726121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21726121 is an equidigital number, since it uses as much as digits as its factorization.

21726121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 336, while the sum is 22.

The square root of 21726121 is about 4661.1287259633. The cubic root of 21726121 is about 279.0363171765.

Adding to 21726121 its reverse (12162712), we get a palindrome (33888833).

The spelling of 21726121 in words is "twenty-one million, seven hundred twenty-six thousand, one hundred twenty-one".