256666221 has 48 divisors (see below), whose sum is σ = 450537984. Its totient is φ = 137452032.

The previous prime is 256666133. The next prime is 256666229. The reversal of 256666221 is 122666652.

It is not a de Polignac number, because 256666221 - 2⁷ = 256666093 is a prime.

It is a super-3 number, since 3×256666221³ (a number of 26 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256666229) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 392731 + ... + 393383.

It is an arithmetic number, because the mean of its divisors is an integer number (9386208).

Almost surely, 2^256666221 is an apocalyptic number.

256666221 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

256666221 is a deficient number, since it is larger than the sum of its proper divisors (193871763).

256666221 is a wasteful number, since it uses less digits than its factorization.

256666221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1050 (or 1047 counting only the distinct ones).

The product of its digits is 51840, while the sum is 36.

The square root of 256666221 is about 16020.8058786067. The cubic root of 256666221 is about 635.5107561171.

The spelling of 256666221 in words is "two hundred fifty-six million, six hundred sixty-six thousand, two hundred twenty-one".