1331631221 has 4 divisors (see below), whose sum is σ = 1367621292. Its totient is φ = 1295641152.

The previous prime is 1331631187. The next prime is 1331631247. The reversal of 1331631221 is 1221361331.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1221361331 = 103 ⋅11857877.

It can be written as a sum of positive squares in 2 ways, for example, as 1273490596 + 58140625 = 35686^2 + 7625^2 .

It is a cyclic number.

It is not a de Polignac number, because 1331631221 - 2³⁰ = 257889397 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1331631421) 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, 17994980 + ... + 17995053.

It is an arithmetic number, because the mean of its divisors is an integer number (341905323).

Almost surely, 2^1331631221 is an apocalyptic number.

It is an amenable number.

1331631221 is a deficient number, since it is larger than the sum of its proper divisors (35990071).

1331631221 is an equidigital number, since it uses as much as digits as its factorization.

1331631221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35990070.

The product of its digits is 648, while the sum is 23.

The square root of 1331631221 is about 36491.5225908703. The cubic root of 1331631221 is about 1100.1738626010.

Adding to 1331631221 its reverse (1221361331), we get a palindrome (2552992552).

The spelling of 1331631221 in words is "one billion, three hundred thirty-one million, six hundred thirty-one thousand, two hundred twenty-one".