21131031 has 16 divisors (see below), whose sum is σ = 29080800. Its totient is φ = 13639680.

The previous prime is 21131029. The next prime is 21131039. The reversal of 21131031 is 13013112.

It is not a de Polignac number, because 21131031 - 2¹ = 21131029 is a prime.

It is a super-2 number, since 2×21131031² = 893040942245922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21130998 and 21131016.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21131039) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17751 + ... + 18903.

It is an arithmetic number, because the mean of its divisors is an integer number (1817550).

Almost surely, 2^21131031 is an apocalyptic number.

21131031 is a deficient number, since it is larger than the sum of its proper divisors (7949769).

21131031 is a wasteful number, since it uses less digits than its factorization.

21131031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1346.

The product of its (nonzero) digits is 18, while the sum is 12.

The square root of 21131031 is about 4596.8501171998. The cubic root of 21131031 is about 276.4650451165.

Adding to 21131031 its reverse (13013112), we get a palindrome (34144143).

The spelling of 21131031 in words is "twenty-one million, one hundred thirty-one thousand, thirty-one".