81720419 has 8 divisors (see below), whose sum is σ = 90611760. Its totient is φ = 73072800.

The previous prime is 81720409. The next prime is 81720427. The reversal of 81720419 is 91402718.

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

It is a cyclic number.

It is not a de Polignac number, because 81720419 - 2¹⁶ = 81654883 is a prime.

It is a super-2 number, since 2×81720419² = 13356453763071122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81720409) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 60224 + ... + 61565.

It is an arithmetic number, because the mean of its divisors is an integer number (11326470).

Almost surely, 2^81720419 is an apocalyptic number.

81720419 is a deficient number, since it is larger than the sum of its proper divisors (8891341).

81720419 is a wasteful number, since it uses less digits than its factorization.

81720419 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 121861.

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 81720419 is about 9039.9346789675. The cubic root of 81720419 is about 433.9538325033.

The spelling of 81720419 in words is "eighty-one million, seven hundred twenty thousand, four hundred nineteen".