231210021 has 16 divisors (see below), whose sum is σ = 353220224. Its totient is φ = 131782464.

The previous prime is 231210019. The next prime is 231210041. The reversal of 231210021 is 120012132.

It is not a de Polignac number, because 231210021 - 2¹ = 231210019 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 231209979 and 231210006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (231210041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5530 + ... + 22203.

It is an arithmetic number, because the mean of its divisors is an integer number (22076264).

Almost surely, 2^231210021 is an apocalyptic number.

231210021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

231210021 is a deficient number, since it is larger than the sum of its proper divisors (122010203).

231210021 is a wasteful number, since it uses less digits than its factorization.

231210021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28140.

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 231210021 is about 15205.5917675045. The cubic root of 231210021 is about 613.7651393376.

Adding to 231210021 its reverse (120012132), we get a palindrome (351222153).

The spelling of 231210021 in words is "two hundred thirty-one million, two hundred ten thousand, twenty-one".