205136831991 has 48 divisors (see below), whose sum is σ = 353699340288. Its totient is φ = 104713560000.

The previous prime is 205136831989. The next prime is 205136831993. The reversal of 205136831991 is 199138631502.

It is an interprime number because it is at equal distance from previous prime (205136831989) and next prime (205136831993).

It is not a de Polignac number, because 205136831991 - 2¹ = 205136831989 is a prime.

It is a super-2 number, since 2×205136831991² (a number of 23 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 205136831991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205136831993) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1672135 + ... + 1790616.

It is an arithmetic number, because the mean of its divisors is an integer number (7368736256).

Almost surely, 2^205136831991 is an apocalyptic number.

205136831991 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

205136831991 is a deficient number, since it is larger than the sum of its proper divisors (148562508297).

205136831991 is a wasteful number, since it uses less digits than its factorization.

205136831991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3462812 (or 3462805 counting only the distinct ones).

The product of its (nonzero) digits is 349920, while the sum is 48.

The spelling of 205136831991 in words is "two hundred five billion, one hundred thirty-six million, eight hundred thirty-one thousand, nine hundred ninety-one".