81721814 has 8 divisors (see below), whose sum is σ = 125191008. Its totient is φ = 39991480.

The previous prime is 81721811. The next prime is 81721819. The reversal of 81721814 is 41812718.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81721811) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 434597 + ... + 434784.

It is an arithmetic number, because the mean of its divisors is an integer number (15648876).

Almost surely, 2^81721814 is an apocalyptic number.

81721814 is a deficient number, since it is larger than the sum of its proper divisors (43469194).

81721814 is a wasteful number, since it uses less digits than its factorization.

81721814 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 869430.

The product of its digits is 3584, while the sum is 32.

The square root of 81721814 is about 9040.0118362754. The cubic root of 81721814 is about 433.9563017440.

The spelling of 81721814 in words is "eighty-one million, seven hundred twenty-one thousand, eight hundred fourteen".