81221545 has 4 divisors (see below), whose sum is σ = 97465860. Its totient is φ = 64977232.

The previous prime is 81221537. The next prime is 81221573. The reversal of 81221545 is 54512218.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 17732521 + 63489024 = 4211^2 + 7968^2 .

It is a cyclic number.

It is not a de Polignac number, because 81221545 - 2³ = 81221537 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8122150 + ... + 8122159.

It is an arithmetic number, because the mean of its divisors is an integer number (24366465).

Almost surely, 2^81221545 is an apocalyptic number.

It is an amenable number.

81221545 is a deficient number, since it is larger than the sum of its proper divisors (16244315).

81221545 is a wasteful number, since it uses less digits than its factorization.

81221545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16244314.

The product of its digits is 3200, while the sum is 28.

The square root of 81221545 is about 9012.2996510325. The cubic root of 81221545 is about 433.0689850566.

The spelling of 81221545 in words is "eighty-one million, two hundred twenty-one thousand, five hundred forty-five".