21331001 has 2 divisors, whose sum is σ = 21331002. Its totient is φ = 21331000.

The previous prime is 21330983. The next prime is 21331021. The reversal of 21331001 is 10013312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20430400 + 900601 = 4520^2 + 949^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21331001 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21331021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10665500 + 10665501.

It is an arithmetic number, because the mean of its divisors is an integer number (10665501).

Almost surely, 2^21331001 is an apocalyptic number.

It is an amenable number.

21331001 is a deficient number, since it is larger than the sum of its proper divisors (1).

21331001 is an equidigital number, since it uses as much as digits as its factorization.

21331001 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 18, while the sum is 11.

The square root of 21331001 is about 4618.5496641262. The cubic root of 21331001 is about 277.3344021868.

Adding to 21331001 its reverse (10013312), we get a palindrome (31344313).

The spelling of 21331001 in words is "twenty-one million, three hundred thirty-one thousand, one".