81220071 has 8 divisors (see below), whose sum is σ = 108346240. Its totient is φ = 54120312.

The previous prime is 81220043. The next prime is 81220081. The reversal of 81220071 is 17002218.

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

It is not a de Polignac number, because 81220071 - 2¹⁷ = 81088999 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81220021) 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, 2286 + ... + 12948.

It is an arithmetic number, because the mean of its divisors is an integer number (13543280).

Almost surely, 2^81220071 is an apocalyptic number.

81220071 is a deficient number, since it is larger than the sum of its proper divisors (27126169).

81220071 is a wasteful number, since it uses less digits than its factorization.

81220071 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13205.

The product of its (nonzero) digits is 224, while the sum is 21.

The square root of 81220071 is about 9012.2178735315. The cubic root of 81220071 is about 433.0663652774.

Adding to 81220071 its reverse (17002218), we get a palindrome (98222289).

The spelling of 81220071 in words is "eighty-one million, two hundred twenty thousand, seventy-one".