1256265666 has 64 divisors (see below), whose sum is σ = 2867477760. Its totient is φ = 407445120.

The previous prime is 1256265641. The next prime is 1256265691. The reversal of 1256265666 is 6665626521.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (1256265641) and next prime (1256265691).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1432020 + ... + 1432896.

It is an arithmetic number, because the mean of its divisors is an integer number (44804340).

Almost surely, 2^1256265666 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1256265666, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1433738880).

1256265666 is an abundant number, since it is smaller than the sum of its proper divisors (1611212094).

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

1256265666 is a wasteful number, since it uses less digits than its factorization.

1256265666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1576 (or 1570 counting only the distinct ones).

The product of its digits is 777600, while the sum is 45.

The square root of 1256265666 is about 35443.8381950939. The cubic root of 1256265666 is about 1079.0142084976.

The spelling of 1256265666 in words is "one billion, two hundred fifty-six million, two hundred sixty-five thousand, six hundred sixty-six".