81721415 has 8 divisors (see below), whose sum is σ = 102329568. Its totient is φ = 62534560.

The previous prime is 81721379. The next prime is 81721429. The reversal of 81721415 is 51412718.

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

It is not a de Polignac number, because 81721415 - 2¹² = 81717319 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 355196 + ... + 355425.

It is an arithmetic number, because the mean of its divisors is an integer number (12791196).

Almost surely, 2^81721415 is an apocalyptic number.

81721415 is a deficient number, since it is larger than the sum of its proper divisors (20608153).

81721415 is a wasteful number, since it uses less digits than its factorization.

81721415 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 710649.

The product of its digits is 2240, while the sum is 29.

The square root of 81721415 is about 9039.9897676933. The cubic root of 81721415 is about 433.9555954909.

The spelling of 81721415 in words is "eighty-one million, seven hundred twenty-one thousand, four hundred fifteen".