21203131 has 4 divisors (see below), whose sum is σ = 22450392. Its totient is φ = 19955872.

The previous prime is 21203129. The next prime is 21203141. The reversal of 21203131 is 13130212.

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 21203131 - 2¹ = 21203129 is a prime.

It is a super-2 number, since 2×21203131² = 899145528406322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21203141) 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, 623605 + ... + 623638.

It is an arithmetic number, because the mean of its divisors is an integer number (5612598).

Almost surely, 2^21203131 is an apocalyptic number.

21203131 is a deficient number, since it is larger than the sum of its proper divisors (1247261).

21203131 is a wasteful number, since it uses less digits than its factorization.

21203131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1247260.

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

The square root of 21203131 is about 4604.6857656088. The cubic root of 21203131 is about 276.7791251019.

Adding to 21203131 its reverse (13130212), we get a palindrome (34333343).

The spelling of 21203131 in words is "twenty-one million, two hundred three thousand, one hundred thirty-one".