1981921855 has 8 divisors (see below), whose sum is σ = 2379312000. Its totient is φ = 1584866976.

The previous prime is 1981921819. The next prime is 1981921859. The reversal of 1981921855 is 5581291891.

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

It is a cyclic number.

It is not a de Polignac number, because 1981921855 - 2¹⁹ = 1981397567 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1981921799 and 1981921808.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981921859) 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, 70620 + ... + 94609.

It is an arithmetic number, because the mean of its divisors is an integer number (297414000).

Almost surely, 2^1981921855 is an apocalyptic number.

1981921855 is a deficient number, since it is larger than the sum of its proper divisors (397390145).

1981921855 is a wasteful number, since it uses less digits than its factorization.

1981921855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 167633.

The product of its digits is 259200, while the sum is 49.

The square root of 1981921855 is about 44518.7809244593. The cubic root of 1981921855 is about 1256.1133815772.

The spelling of 1981921855 in words is "one billion, nine hundred eighty-one million, nine hundred twenty-one thousand, eight hundred fifty-five".