3121721331 has 4 divisors (see below), whose sum is σ = 4162295112. Its totient is φ = 2081147552.

The previous prime is 3121721321. The next prime is 3121721399. The reversal of 3121721331 is 1331271213.

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 3121721331 - 2¹⁷ = 3121590259 is a prime.

It is a super-2 number, since 2×3121721331² = 19490288136840823122, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (3121721311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 520286886 + ... + 520286891.

It is an arithmetic number, because the mean of its divisors is an integer number (1040573778).

Almost surely, 2^3121721331 is an apocalyptic number.

3121721331 is a deficient number, since it is larger than the sum of its proper divisors (1040573781).

3121721331 is a wasteful number, since it uses less digits than its factorization.

3121721331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1040573780.

The product of its digits is 756, while the sum is 24.

The square root of 3121721331 is about 55872.3664345802. The cubic root of 3121721331 is about 1461.4973895843.

Adding to 3121721331 its reverse (1331271213), we get a palindrome (4452992544).

The spelling of 3121721331 in words is "three billion, one hundred twenty-one million, seven hundred twenty-one thousand, three hundred thirty-one".