81621895471 has 4 divisors (see below), whose sum is σ = 82384717032. Its totient is φ = 80859073912.

The previous prime is 81621895441. The next prime is 81621895493. The reversal of 81621895471 is 17459812618.

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 81621895471 - 2⁷ = 81621895343 is a prime.

It is a super-3 number, since 3×81621895471³ (a number of 34 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81621895441) 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, 381410620 + ... + 381410833.

It is an arithmetic number, because the mean of its divisors is an integer number (20596179258).

Almost surely, 2^81621895471 is an apocalyptic number.

81621895471 is a deficient number, since it is larger than the sum of its proper divisors (762821561).

81621895471 is a wasteful number, since it uses less digits than its factorization.

81621895471 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 762821560.

The product of its digits is 967680, while the sum is 52.

The spelling of 81621895471 in words is "eighty-one billion, six hundred twenty-one million, eight hundred ninety-five thousand, four hundred seventy-one".