21021331 has 2 divisors, whose sum is σ = 21021332. Its totient is φ = 21021330.

The previous prime is 21021323. The next prime is 21021349. The reversal of 21021331 is 13312012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21021331 - 2³ = 21021323 is a prime.

It is a super-2 number, since 2×21021331² = 883792714023122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21021431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510665 + 10510666.

It is an arithmetic number, because the mean of its divisors is an integer number (10510666).

Almost surely, 2^21021331 is an apocalyptic number.

21021331 is a deficient number, since it is larger than the sum of its proper divisors (1).

21021331 is an equidigital number, since it uses as much as digits as its factorization.

21021331 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 21021331 is about 4584.9025071423. The cubic root of 21021331 is about 275.9857996965.

Adding to 21021331 its reverse (13312012), we get a palindrome (34333343).

The spelling of 21021331 in words is "twenty-one million, twenty-one thousand, three hundred thirty-one".