19640618391981 has 8 divisors (see below), whose sum is σ = 26187973885024. Its totient is φ = 13093504246800.

The previous prime is 19640618391973. The next prime is 19640618392061. The reversal of 19640618391981 is 18919381604691.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 19640618391981 - 2³ = 19640618391973 is a prime.

It is a super-2 number, since 2×19640618391981² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19640618391181) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 60146995 + ... + 60472656.

It is an arithmetic number, because the mean of its divisors is an integer number (3273496735628).

Almost surely, 2^{19640618391981} is an apocalyptic number.

It is an amenable number.

19640618391981 is a deficient number, since it is larger than the sum of its proper divisors (6547355493043).

19640618391981 is a wasteful number, since it uses less digits than its factorization.

19640618391981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 120673931.

The product of its (nonzero) digits is 20155392, while the sum is 66.

The spelling of 19640618391981 in words is "nineteen trillion, six hundred forty billion, six hundred eighteen million, three hundred ninety-one thousand, nine hundred eighty-one".