1231508221 has 2 divisors, whose sum is σ = 1231508222. Its totient is φ = 1231508220.

The previous prime is 1231508209. The next prime is 1231508249. The reversal of 1231508221 is 1228051321.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1048852996 + 182655225 = 32386^2 + 13515^2 .

It is a cyclic number.

It is not a de Polignac number, because 1231508221 - 2⁵ = 1231508189 is a prime.

It is a super-2 number, since 2×1231508221² = 3033224996781169682, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1231578221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 615754110 + 615754111.

It is an arithmetic number, because the mean of its divisors is an integer number (615754111).

Almost surely, 2^1231508221 is an apocalyptic number.

It is an amenable number.

1231508221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1231508221 is an equidigital number, since it uses as much as digits as its factorization.

1231508221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 1231508221 is about 35092.8514230463. The cubic root of 1231508221 is about 1071.8790231255.

Adding to 1231508221 its reverse (1228051321), we get a palindrome (2459559542).

The spelling of 1231508221 in words is "one billion, two hundred thirty-one million, five hundred eight thousand, two hundred twenty-one".