1531255166821 has 2 divisors, whose sum is σ = 1531255166822. Its totient is φ = 1531255166820.

The previous prime is 1531255166783. The next prime is 1531255166879. The reversal of 1531255166821 is 1286615521351.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1530945934596 + 309232225 = 1237314^2 + 17585^2 .

It is a cyclic number.

It is not a de Polignac number, because 1531255166821 - 2¹⁷ = 1531255035749 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1531255166891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 765627583410 + 765627583411.

It is an arithmetic number, because the mean of its divisors is an integer number (765627583411).

Almost surely, 2^{1531255166821} is an apocalyptic number.

It is an amenable number.

1531255166821 is a deficient number, since it is larger than the sum of its proper divisors (1).

1531255166821 is an equidigital number, since it uses as much as digits as its factorization.

1531255166821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 432000, while the sum is 46.

The spelling of 1531255166821 in words is "one trillion, five hundred thirty-one billion, two hundred fifty-five million, one hundred sixty-six thousand, eight hundred twenty-one".