1287745981 has 4 divisors (see below), whose sum is σ = 1287863712. Its totient is φ = 1287628252.

The previous prime is 1287745973. The next prime is 1287746021. The reversal of 1287745981 is 1895477821.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1895477821 = 2671 ⋅709651.

It is a cyclic number.

It is not a de Polignac number, because 1287745981 - 2³ = 1287745973 is a prime.

It is a super-2 number, since 2×1287745981² = 3316579423163304722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1287745961) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40561 + ... + 64966.

It is an arithmetic number, because the mean of its divisors is an integer number (321965928).

Almost surely, 2^1287745981 is an apocalyptic number.

It is an amenable number.

1287745981 is a deficient number, since it is larger than the sum of its proper divisors (117731).

1287745981 is a wasteful number, since it uses less digits than its factorization.

1287745981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117730.

The product of its digits is 1128960, while the sum is 52.

The square root of 1287745981 is about 35885.1777339893. The cubic root of 1287745981 is about 1087.9528337599.

The spelling of 1287745981 in words is "one billion, two hundred eighty-seven million, seven hundred forty-five thousand, nine hundred eighty-one".