1981958156685 has 64 divisors (see below), whose sum is σ = 3817797984000. Its totient is φ = 969747012864.

The previous prime is 1981958156603. The next prime is 1981958156719. The reversal of 1981958156685 is 5866518591891.

1981958156685 is a `hidden beast` number, since 1 + 9 + 8 + 1 + 9 + 58 + 1 + 566 + 8 + 5 = 666.

It is not a de Polignac number, because 1981958156685 - 2⁷ = 1981958156557 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 3178110 + ... + 3750239.

It is an arithmetic number, because the mean of its divisors is an integer number (59653093500).

Almost surely, 2^{1981958156685} is an apocalyptic number.

1981958156685 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1981958156685 is a deficient number, since it is larger than the sum of its proper divisors (1835839827315).

1981958156685 is a wasteful number, since it uses less digits than its factorization.

1981958156685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6928539 (or 6928533 counting only the distinct ones).

The product of its digits is 186624000, while the sum is 72.

The spelling of 1981958156685 in words is "one trillion, nine hundred eighty-one billion, nine hundred fifty-eight million, one hundred fifty-six thousand, six hundred eighty-five".