1265721851 has 2 divisors, whose sum is σ = 1265721852. Its totient is φ = 1265721850.

The previous prime is 1265721829. The next prime is 1265721881. The reversal of 1265721851 is 1581275621.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1265721851 - 2¹⁸ = 1265459707 is a prime.

It is not a weakly prime, because it can be changed into another prime (1265721881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 632860925 + 632860926.

It is an arithmetic number, because the mean of its divisors is an integer number (632860926).

Almost surely, 2^1265721851 is an apocalyptic number.

1265721851 is a deficient number, since it is larger than the sum of its proper divisors (1).

1265721851 is an equidigital number, since it uses as much as digits as its factorization.

1265721851 is an evil number, because the sum of its binary digits is even.

The product of its digits is 33600, while the sum is 38.

The square root of 1265721851 is about 35576.9848497593. The cubic root of 1265721851 is about 1081.7147687923.

The spelling of 1265721851 in words is "one billion, two hundred sixty-five million, seven hundred twenty-one thousand, eight hundred fifty-one".