2561721266 has 24 divisors (see below), whose sum is σ = 4176405504. Its totient is φ = 1177927920.

The previous prime is 2561721257. The next prime is 2561721271. The reversal of 2561721266 is 6621271652.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 77615 + ... + 105581.

It is an arithmetic number, because the mean of its divisors is an integer number (174016896).

Almost surely, 2^2561721266 is an apocalyptic number.

2561721266 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

2561721266 is a deficient number, since it is larger than the sum of its proper divisors (1614684238).

2561721266 is a wasteful number, since it uses less digits than its factorization.

2561721266 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28266 (or 28253 counting only the distinct ones).

The product of its digits is 60480, while the sum is 38.

The square root of 2561721266 is about 50613.4494576293. The cubic root of 2561721266 is about 1368.2872848452.

The spelling of 2561721266 in words is "two billion, five hundred sixty-one million, seven hundred twenty-one thousand, two hundred sixty-six".