21003131 has 4 divisors (see below), whose sum is σ = 21012432. Its totient is φ = 20993832.

The previous prime is 21003121. The next prime is 21003139. The reversal of 21003131 is 13130012.

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 21003131 - 2¹⁴ = 20986747 is a prime.

It is a super-2 number, since 2×21003131² = 882263023606322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21003139) 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, 1145 + ... + 6581.

It is an arithmetic number, because the mean of its divisors is an integer number (5253108).

Almost surely, 2^21003131 is an apocalyptic number.

21003131 is a deficient number, since it is larger than the sum of its proper divisors (9301).

21003131 is an equidigital number, since it uses as much as digits as its factorization.

21003131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9300.

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

The square root of 21003131 is about 4582.9173023305. The cubic root of 21003131 is about 275.9061283720.

Adding to 21003131 its reverse (13130012), we get a palindrome (34133143).

The spelling of 21003131 in words is "twenty-one million, three thousand, one hundred thirty-one".