1288821861 has 10 divisors (see below), whose sum is σ = 1925277222. Its totient is φ = 859214520.

The previous prime is 1288821841. The next prime is 1288821881. The reversal of 1288821861 is 1681288821.

It is an interprime number because it is at equal distance from previous prime (1288821841) and next prime (1288821881).

It can be written as a sum of positive squares in only one way, i.e., 1079122500 + 209699361 = 32850^2 + 14481^2 .

It is not a de Polignac number, because 1288821861 - 2⁹ = 1288821349 is a prime.

It is a super-2 number, since 2×1288821861² = 3322123578783006642, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1288821811) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 7955610 + ... + 7955771.

Almost surely, 2^1288821861 is an apocalyptic number.

It is an amenable number.

1288821861 is a deficient number, since it is larger than the sum of its proper divisors (636455361).

1288821861 is an equidigital number, since it uses as much as digits as its factorization.

1288821861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15911393 (or 15911384 counting only the distinct ones).

The product of its digits is 98304, while the sum is 45.

The square root of 1288821861 is about 35900.1651946060. The cubic root of 1288821861 is about 1088.2557353380.

The spelling of 1288821861 in words is "one billion, two hundred eighty-eight million, eight hundred twenty-one thousand, eight hundred sixty-one".