9987121657831 has 2 divisors, whose sum is σ = 9987121657832. Its totient is φ = 9987121657830.

The previous prime is 9987121657819. The next prime is 9987121657889. The reversal of 9987121657831 is 1387561217899.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 9987121657831 - 2²¹ = 9987119560679 is a prime.

It is a super-2 number, since 2×9987121657831² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9987121657801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4993560828915 + 4993560828916.

It is an arithmetic number, because the mean of its divisors is an integer number (4993560828916).

Almost surely, 2^{9987121657831} is an apocalyptic number.

9987121657831 is a deficient number, since it is larger than the sum of its proper divisors (1).

9987121657831 is an equidigital number, since it uses as much as digits as its factorization.

9987121657831 is an evil number, because the sum of its binary digits is even.

The product of its digits is 45722880, while the sum is 67.

The spelling of 9987121657831 in words is "nine trillion, nine hundred eighty-seven billion, one hundred twenty-one million, six hundred fifty-seven thousand, eight hundred thirty-one".