81972419 has 4 divisors (see below), whose sum is σ = 86794344. Its totient is φ = 77150496.

The previous prime is 81972409. The next prime is 81972421. The reversal of 81972419 is 91427918.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81972419 - 2¹⁶ = 81906883 is a prime.

It is a super-2 number, since 2×81972419² = 13438954953423122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81972409) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2410937 + ... + 2410970.

It is an arithmetic number, because the mean of its divisors is an integer number (21698586).

Almost surely, 2^81972419 is an apocalyptic number.

81972419 is a deficient number, since it is larger than the sum of its proper divisors (4821925).

81972419 is a wasteful number, since it uses less digits than its factorization.

81972419 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4821924.

The product of its digits is 36288, while the sum is 41.

The square root of 81972419 is about 9053.8621040968. The cubic root of 81972419 is about 434.3994337066.

The spelling of 81972419 in words is "eighty-one million, nine hundred seventy-two thousand, four hundred nineteen".