81655221 has 8 divisors (see below), whose sum is σ = 113607360. Its totient is φ = 52069952.

The previous prime is 81655201. The next prime is 81655247. The reversal of 81655221 is 12255618.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81655221 - 2⁶ = 81655157 is a prime.

It is a super-3 number, since 3×81655221³ (a number of 25 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81655201) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 591636 + ... + 591773.

It is an arithmetic number, because the mean of its divisors is an integer number (14200920).

Almost surely, 2^81655221 is an apocalyptic number.

It is an amenable number.

81655221 is a deficient number, since it is larger than the sum of its proper divisors (31952139).

81655221 is a wasteful number, since it uses less digits than its factorization.

81655221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1183435.

The product of its digits is 4800, while the sum is 30.

The square root of 81655221 is about 9036.3278492981. The cubic root of 81655221 is about 433.8383964436.

The spelling of 81655221 in words is "eighty-one million, six hundred fifty-five thousand, two hundred twenty-one".