21311403 has 4 divisors (see below), whose sum is σ = 28415208. Its totient is φ = 14207600.

The previous prime is 21311399. The next prime is 21311413. The reversal of 21311403 is 30411312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21311403 - 2² = 21311399 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21311413) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3551898 + ... + 3551903.

It is an arithmetic number, because the mean of its divisors is an integer number (7103802).

Almost surely, 2^21311403 is an apocalyptic number.

21311403 is a deficient number, since it is larger than the sum of its proper divisors (7103805).

21311403 is an equidigital number, since it uses as much as digits as its factorization.

21311403 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7103804.

The product of its (nonzero) digits is 72, while the sum is 15.

The square root of 21311403 is about 4616.4275148647. The cubic root of 21311403 is about 277.2494418825.

Adding to 21311403 its reverse (30411312), we get a palindrome (51722715).

Subtracting 21311403 from its reverse (30411312), we obtain a palindrome (9099909).

The spelling of 21311403 in words is "twenty-one million, three hundred eleven thousand, four hundred three".