21040031 has 4 divisors (see below), whose sum is σ = 21079464. Its totient is φ = 21000600.

The previous prime is 21040007. The next prime is 21040039. The reversal of 21040031 is 13004012.

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 21040031 - 2²² = 16845727 is a prime.

It is a super-2 number, since 2×21040031² = 885365808961922, 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 = 21039994 and 21040021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21040039) 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, 18905 + ... + 19986.

It is an arithmetic number, because the mean of its divisors is an integer number (5269866).

Almost surely, 2^21040031 is an apocalyptic number.

21040031 is a deficient number, since it is larger than the sum of its proper divisors (39433).

21040031 is an equidigital number, since it uses as much as digits as its factorization.

21040031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39432.

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 21040031 is about 4586.9413556312. The cubic root of 21040031 is about 276.0676119101.

Adding to 21040031 its reverse (13004012), we get a palindrome (34044043).

The spelling of 21040031 in words is "twenty-one million, forty thousand, thirty-one".