1265987871921 has 8 divisors (see below), whose sum is σ = 1690617191904. Its totient is φ = 842675233280.

The previous prime is 1265987871901. The next prime is 1265987871961. The reversal of 1265987871921 is 1291787895621.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1265987871921 - 2⁷ = 1265987871793 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1265987871901) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 329168091 + ... + 329171936.

It is an arithmetic number, because the mean of its divisors is an integer number (211327148988).

Almost surely, 2^{1265987871921} is an apocalyptic number.

It is an amenable number.

1265987871921 is a deficient number, since it is larger than the sum of its proper divisors (424629319983).

1265987871921 is an equidigital number, since it uses as much as digits as its factorization.

1265987871921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 658340671.

The product of its digits is 30481920, while the sum is 66.

The spelling of 1265987871921 in words is "one trillion, two hundred sixty-five billion, nine hundred eighty-seven million, eight hundred seventy-one thousand, nine hundred twenty-one".