81221487 has 16 divisors (see below), whose sum is σ = 114696960. Its totient is φ = 51017472.

The previous prime is 81221471. The next prime is 81221507. The reversal of 81221487 is 78412218.

It is a happy number.

It is not a de Polignac number, because 81221487 - 2⁴ = 81221471 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81221407) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4162 + ... + 13407.

It is an arithmetic number, because the mean of its divisors is an integer number (7168560).

Almost surely, 2^81221487 is an apocalyptic number.

81221487 is a deficient number, since it is larger than the sum of its proper divisors (33475473).

81221487 is a wasteful number, since it uses less digits than its factorization.

81221487 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17662.

The product of its digits is 7168, while the sum is 33.

The square root of 81221487 is about 9012.2964332072. The cubic root of 81221487 is about 433.0688819722.

The spelling of 81221487 in words is "eighty-one million, two hundred twenty-one thousand, four hundred eighty-seven".