81721107 has 12 divisors (see below), whose sum is σ = 127121904. Its totient is φ = 50289840.

The previous prime is 81721103. The next prime is 81721121. The reversal of 81721107 is 70112718.

It is not a de Polignac number, because 81721107 - 2² = 81721103 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81721103) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 349119 + ... + 349352.

It is an arithmetic number, because the mean of its divisors is an integer number (10593492).

Almost surely, 2^81721107 is an apocalyptic number.

81721107 is a deficient number, since it is larger than the sum of its proper divisors (45400797).

81721107 is a wasteful number, since it uses less digits than its factorization.

81721107 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 698490 (or 698487 counting only the distinct ones).

The product of its (nonzero) digits is 784, while the sum is 27.

The square root of 81721107 is about 9039.9727322598. The cubic root of 81721107 is about 433.9550503115.

The spelling of 81721107 in words is "eighty-one million, seven hundred twenty-one thousand, one hundred seven".