81210555 has 24 divisors (see below), whose sum is σ = 141195600. Its totient is φ = 43179840.

The previous prime is 81210511. The next prime is 81210587. The reversal of 81210555 is 55501218.

It is not a de Polignac number, because 81210555 - 2¹⁷ = 81079483 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 13120 + ... + 18290.

It is an arithmetic number, because the mean of its divisors is an integer number (5883150).

Almost surely, 2^81210555 is an apocalyptic number.

81210555 is a deficient number, since it is larger than the sum of its proper divisors (59985045).

81210555 is a wasteful number, since it uses less digits than its factorization.

81210555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5531 (or 5528 counting only the distinct ones).

The product of its (nonzero) digits is 2000, while the sum is 27.

The square root of 81210555 is about 9011.6899081138. The cubic root of 81210555 is about 433.0494514758.

The spelling of 81210555 in words is "eighty-one million, two hundred ten thousand, five hundred fifty-five".