21311603 has 2 divisors, whose sum is σ = 21311604. Its totient is φ = 21311602.

The previous prime is 21311599. The next prime is 21311611. The reversal of 21311603 is 30611312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21311603 - 2² = 21311599 is a prime.

It is not a weakly prime, because it can be changed into another prime (21311623) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10655801 + 10655802.

It is an arithmetic number, because the mean of its divisors is an integer number (10655802).

Almost surely, 2^21311603 is an apocalyptic number.

21311603 is a deficient number, since it is larger than the sum of its proper divisors (1).

21311603 is an equidigital number, since it uses as much as digits as its factorization.

21311603 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 108, while the sum is 17.

The square root of 21311603 is about 4616.4491765858. The cubic root of 21311603 is about 277.2503091759.

Adding to 21311603 its reverse (30611312), we get a palindrome (51922915).

The spelling of 21311603 in words is "twenty-one million, three hundred eleven thousand, six hundred three".