1165561551 has 24 divisors (see below), whose sum is σ = 2099021184. Its totient is φ = 605486160.

The previous prime is 1165561541. The next prime is 1165561561. The reversal of 1165561551 is 1551655611.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (1165561541) and next prime (1165561561).

It is not a de Polignac number, because 1165561551 - 2⁶ = 1165561487 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1165561511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 840261 + ... + 841646.

It is an arithmetic number, because the mean of its divisors is an integer number (87459216).

Almost surely, 2^1165561551 is an apocalyptic number.

1165561551 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1165561551 is a deficient number, since it is larger than the sum of its proper divisors (933459633).

1165561551 is a wasteful number, since it uses less digits than its factorization.

1165561551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1681931 (or 1681928 counting only the distinct ones).

The product of its digits is 22500, while the sum is 36.

The square root of 1165561551 is about 34140.3214835479. The cubic root of 1165561551 is about 1052.3940989845.

The spelling of 1165561551 in words is "one billion, one hundred sixty-five million, five hundred sixty-one thousand, five hundred fifty-one".