1191801551 has 4 divisors (see below), whose sum is σ = 1192018104. Its totient is φ = 1191585000.

The previous prime is 1191801521. The next prime is 1191801563. The reversal of 1191801551 is 1551081911.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1191801551 - 2¹⁸ = 1191539407 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1191801521) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 99800 + ... + 111101.

It is an arithmetic number, because the mean of its divisors is an integer number (298004526).

Almost surely, 2^1191801551 is an apocalyptic number.

1191801551 is a deficient number, since it is larger than the sum of its proper divisors (216553).

1191801551 is an equidigital number, since it uses as much as digits as its factorization.

1191801551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 216552.

The product of its (nonzero) digits is 1800, while the sum is 32.

The square root of 1191801551 is about 34522.4789231596. The cubic root of 1191801551 is about 1060.2329946470.

The spelling of 1191801551 in words is "one billion, one hundred ninety-one million, eight hundred one thousand, five hundred fifty-one".