81001620 has 144 divisors (see below), whose sum is σ = 291328128. Its totient is φ = 18506880.

The previous prime is 81001597. The next prime is 81001639. The reversal of 81001620 is 2610018.

It is a super-2 number, since 2×81001620² = 13122524885248800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 81001593 and 81001602.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 32830 + ... + 35210.

It is an arithmetic number, because the mean of its divisors is an integer number (2023112).

Almost surely, 2^81001620 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81001620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (145664064).

81001620 is an abundant number, since it is smaller than the sum of its proper divisors (210326508).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81001620 is a wasteful number, since it uses less digits than its factorization.

81001620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2412 (or 2398 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 18.

The square root of 81001620 is about 9000.0899995500. The cubic root of 81001620 is about 432.6777555721.

Adding to 81001620 its reverse (2610018), we get a palindrome (83611638).

The spelling of 81001620 in words is "eighty-one million, one thousand, six hundred twenty".