1231000021 has 4 divisors (see below), whose sum is σ = 1231860492. Its totient is φ = 1230139552.

The previous prime is 1231000009. The next prime is 1231000037. The reversal of 1231000021 is 1200001321.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 556299396 + 674700625 = 23586^2 + 25975^2 .

It is a cyclic number.

It is not a de Polignac number, because 1231000021 - 2⁵ = 1230999989 is a prime.

It is a super-2 number, since 2×1231000021² = 3030722103404000882, 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 = 1230999971 and 1231000007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1231000051) 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 3 ways as a sum of consecutive naturals, for example, 428086 + ... + 430951.

It is an arithmetic number, because the mean of its divisors is an integer number (307965123).

Almost surely, 2^1231000021 is an apocalyptic number.

It is an amenable number.

1231000021 is a deficient number, since it is larger than the sum of its proper divisors (860471).

1231000021 is an equidigital number, since it uses as much as digits as its factorization.

1231000021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 860470.

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

The square root of 1231000021 is about 35085.6098849657. The cubic root of 1231000021 is about 1071.7315606191.

Adding to 1231000021 its reverse (1200001321), we get a palindrome (2431001342).

The spelling of 1231000021 in words is "one billion, two hundred thirty-one million, twenty-one", and thus it is an aban number.