1215561765 has 96 divisors (see below), whose sum is σ = 2279088000. Its totient is φ = 551232000.

The previous prime is 1215561757. The next prime is 1215561769. The reversal of 1215561765 is 5671655121.

It is a happy number.

It is not a de Polignac number, because 1215561765 - 2³ = 1215561757 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1215561769) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 3482811 + ... + 3483159.

It is an arithmetic number, because the mean of its divisors is an integer number (23740500).

Almost surely, 2^1215561765 is an apocalyptic number.

1215561765 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1215561765 is a deficient number, since it is larger than the sum of its proper divisors (1063526235).

1215561765 is a wasteful number, since it uses less digits than its factorization.

1215561765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 499 (or 488 counting only the distinct ones).

The product of its digits is 63000, while the sum is 39.

The square root of 1215561765 is about 34864.9073568251. The cubic root of 1215561765 is about 1067.2324218239.

It can be divided in two parts, 121556 and 1765, that added together give a palindrome (123321).

The spelling of 1215561765 in words is "one billion, two hundred fifteen million, five hundred sixty-one thousand, seven hundred sixty-five".