1266721720 has 64 divisors (see below), whose sum is σ = 3128025600. Its totient is φ = 457841280.

The previous prime is 1266721717. The next prime is 1266721723. The reversal of 1266721720 is 271276621.

It is an interprime number because it is at equal distance from previous prime (1266721717) and next prime (1266721723).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1266721723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 64861 + ... + 82099.

It is an arithmetic number, because the mean of its divisors is an integer number (48875400).

Almost surely, 2^1266721720 is an apocalyptic number.

1266721720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1266721720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1564012800).

1266721720 is an abundant number, since it is smaller than the sum of its proper divisors (1861303880).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1266721720 is a wasteful number, since it uses less digits than its factorization.

1266721720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17428 (or 17424 counting only the distinct ones).

The product of its (nonzero) digits is 14112, while the sum is 34.

The square root of 1266721720 is about 35591.0342642638. The cubic root of 1266721720 is about 1081.9995307745. Note that the first 3 decimals are identical.

The spelling of 1266721720 in words is "one billion, two hundred sixty-six million, seven hundred twenty-one thousand, seven hundred twenty".