21120031 has 4 divisors (see below), whose sum is σ = 21238200. Its totient is φ = 21001864.

The previous prime is 21120019. The next prime is 21120041. The reversal of 21120031 is 13002112.

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 21120031 - 2⁵ = 21119999 is a prime.

It is a super-3 number, since 3×21120031³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21120041) 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, 58816 + ... + 59173.

It is an arithmetic number, because the mean of its divisors is an integer number (5309550).

Almost surely, 2^21120031 is an apocalyptic number.

21120031 is a deficient number, since it is larger than the sum of its proper divisors (118169).

21120031 is a wasteful number, since it uses less digits than its factorization.

21120031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 118168.

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

The square root of 21120031 is about 4595.6534899838. The cubic root of 21120031 is about 276.4170644422.

Adding to 21120031 its reverse (13002112), we get a palindrome (34122143).

The spelling of 21120031 in words is "twenty-one million, one hundred twenty thousand, thirty-one".