21645101 has 2 divisors, whose sum is σ = 21645102. Its totient is φ = 21645100.

The previous prime is 21645079. The next prime is 21645103. The reversal of 21645101 is 10154612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13147876 + 8497225 = 3626^2 + 2915^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21645101 is a prime.

Together with 21645103, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21645103) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10822550 + 10822551.

It is an arithmetic number, because the mean of its divisors is an integer number (10822551).

Almost surely, 2^21645101 is an apocalyptic number.

It is an amenable number.

21645101 is a deficient number, since it is larger than the sum of its proper divisors (1).

21645101 is an equidigital number, since it uses as much as digits as its factorization.

21645101 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 240, while the sum is 20.

The square root of 21645101 is about 4652.4295803376. The cubic root of 21645101 is about 278.6890288735.

Adding to 21645101 its reverse (10154612), we get a palindrome (31799713).

The spelling of 21645101 in words is "twenty-one million, six hundred forty-five thousand, one hundred one".