1215191988 has 36 divisors (see below), whose sum is σ = 3177659940. Its totient is φ = 391095936.

The previous prime is 1215191981. The next prime is 1215191993. The reversal of 1215191988 is 8891915121.

1215191988 is a `hidden beast` number, since 121 + 519 + 1 + 9 + 8 + 8 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 842624784 + 372567204 = 29028^2 + 19302^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1215191981) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 580945 + ... + 583032.

Almost surely, 2^1215191988 is an apocalyptic number.

1215191988 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is an amenable number.

1215191988 is an abundant number, since it is smaller than the sum of its proper divisors (1962467952).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1215191988 is a wasteful number, since it uses less digits than its factorization.

1215191988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1164016 (or 1164011 counting only the distinct ones).

The product of its digits is 51840, while the sum is 45.

The square root of 1215191988 is about 34859.6039564422. The cubic root of 1215191988 is about 1067.1241925706.

The spelling of 1215191988 in words is "one billion, two hundred fifteen million, one hundred ninety-one thousand, nine hundred eighty-eight".