21243031 has 4 divisors (see below), whose sum is σ = 21441672. Its totient is φ = 21044392.

The previous prime is 21243023. The next prime is 21243049. The reversal of 21243031 is 13034212.

It is a happy number.

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 21243031 - 2³ = 21243023 is a prime.

It is a super-2 number, since 2×21243031² = 902532732133922, 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 = 21242996 and 21243014.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21243011) 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, 99160 + ... + 99373.

It is an arithmetic number, because the mean of its divisors is an integer number (5360418).

Almost surely, 2^21243031 is an apocalyptic number.

21243031 is a deficient number, since it is larger than the sum of its proper divisors (198641).

21243031 is a wasteful number, since it uses less digits than its factorization.

21243031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 198640.

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 21243031 is about 4609.0162724816. The cubic root of 21243031 is about 276.9526304068.

Adding to 21243031 its reverse (13034212), we get a palindrome (34277243).

The spelling of 21243031 in words is "twenty-one million, two hundred forty-three thousand, thirty-one".