1286384687721 has 189 divisors, whose sum is σ = 2390093197941. Its totient is φ = 689877264384.

The previous prime is 1286384687711. The next prime is 1286384687743. The reversal of 1286384687721 is 1277864836821.

It is a happy number.

The square root of 1286384687721 is 1134189.

It is a perfect power (a square), and thus also a powerful number.

1286384687721 is a `hidden beast` number, since 1 + 2 + 86 + 3 + 8 + 468 + 77 + 21 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 51352545321 + 1235032142400 = 226611^2 + 1111320^2 .

It is a tau number, because it is divible by the number of its divisors (189).

It is not a de Polignac number, because 1286384687721 - 2²⁷ = 1286250469993 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is not an unprimeable number, because it can be changed into a prime (1286384687711) by changing a digit.

It is a polite number, since it can be written in 188 ways as a sum of consecutive naturals, for example, 3644149081 + ... + 3644149433.

Almost surely, 2^{1286384687721} is an apocalyptic number.

1286384687721 is the 1134189-th square number.

1286384687721 is the 567095-th centered octagonal number.

It is an amenable number.

1286384687721 is a deficient number, since it is larger than the sum of its proper divisors (1103708510220).

1286384687721 is an frugal number, since it uses more digits than its factorization.

1286384687721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 772 (or 380 counting only the distinct ones).

The product of its digits is 43352064, while the sum is 63.

The spelling of 1286384687721 in words is "one trillion, two hundred eighty-six billion, three hundred eighty-four million, six hundred eighty-seven thousand, seven hundred twenty-one".