1991551105 has 8 divisors (see below), whose sum is σ = 2530441512. Its totient is φ = 1499520768.

The previous prime is 1991551103. The next prime is 1991551109. The reversal of 1991551105 is 5011551991.

It can be written as a sum of positive squares in 4 ways, for example, as 117007489 + 1874543616 = 10817^2 + 43296^2 .

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

It is not a de Polignac number, because 1991551105 - 2¹ = 1991551103 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991551103) 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, 11714922 + ... + 11715091.

It is an arithmetic number, because the mean of its divisors is an integer number (316305189).

Almost surely, 2^1991551105 is an apocalyptic number.

It is an amenable number.

1991551105 is a deficient number, since it is larger than the sum of its proper divisors (538890407).

1991551105 is a wasteful number, since it uses less digits than its factorization.

1991551105 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23430035.

The product of its (nonzero) digits is 10125, while the sum is 37.

The square root of 1991551105 is about 44626.7980590138. The cubic root of 1991551105 is about 1258.1443889612.

The spelling of 1991551105 in words is "one billion, nine hundred ninety-one million, five hundred fifty-one thousand, one hundred five".