21231031 has 4 divisors (see below), whose sum is σ = 21331864. Its totient is φ = 21130200.

The previous prime is 21231029. The next prime is 21231107. The reversal of 21231031 is 13013212.

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 21231031 - 2¹ = 21231029 is a prime.

It is a super-2 number, since 2×21231031² = 901513354645922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21231631) 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, 50100 + ... + 50521.

It is an arithmetic number, because the mean of its divisors is an integer number (5332966).

Almost surely, 2^21231031 is an apocalyptic number.

21231031 is a deficient number, since it is larger than the sum of its proper divisors (100833).

21231031 is a wasteful number, since it uses less digits than its factorization.

21231031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 100832.

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

The square root of 21231031 is about 4607.7142923580. The cubic root of 21231031 is about 276.9004712217.

Adding to 21231031 its reverse (13013212), we get a palindrome (34244243).

The spelling of 21231031 in words is "twenty-one million, two hundred thirty-one thousand, thirty-one".