21731603 has 4 divisors (see below), whose sum is σ = 21742440. Its totient is φ = 21720768.

The previous prime is 21731597. The next prime is 21731621. The reversal of 21731603 is 30613712.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21731603 - 2⁴ = 21731587 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21731623) 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, 1433 + ... + 6746.

It is an arithmetic number, because the mean of its divisors is an integer number (5435610).

Almost surely, 2^21731603 is an apocalyptic number.

21731603 is a deficient number, since it is larger than the sum of its proper divisors (10837).

21731603 is an equidigital number, since it uses as much as digits as its factorization.

21731603 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10836.

The product of its (nonzero) digits is 756, while the sum is 23.

The square root of 21731603 is about 4661.7167438616. The cubic root of 21731603 is about 279.0597842962.

The spelling of 21731603 in words is "twenty-one million, seven hundred thirty-one thousand, six hundred three".