21102031 has 4 divisors (see below), whose sum is σ = 21311064. Its totient is φ = 20893000.

The previous prime is 21102023. The next prime is 21102047. The reversal of 21102031 is 13020112.

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 21102031 - 2³ = 21102023 is a prime.

It is a super-2 number, since 2×21102031² = 890591424649922, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21101999 and 21102017.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21102071) 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, 104365 + ... + 104566.

It is an arithmetic number, because the mean of its divisors is an integer number (5327766).

Almost surely, 2^21102031 is an apocalyptic number.

21102031 is a deficient number, since it is larger than the sum of its proper divisors (209033).

21102031 is a wasteful number, since it uses less digits than its factorization.

21102031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 209032.

The product of its (nonzero) digits is 12, while the sum is 10.

The square root of 21102031 is about 4593.6947003474. The cubic root of 21102031 is about 276.3385146629.

Adding to 21102031 its reverse (13020112), we get a palindrome (34122143).

The spelling of 21102031 in words is "twenty-one million, one hundred two thousand, thirty-one".