81061920 has 144 divisors (see below), whose sum is σ = 283577112. Its totient is φ = 21073920.

The previous prime is 81061919. The next prime is 81061921. The reversal of 81061920 is 2916018.

It is an interprime number because it is at equal distance from previous prime (81061919) and next prime (81061921).

It can be written as a sum of positive squares in 4 ways, for example, as 68359824 + 12702096 = 8268^2 + 3564^2 .

It is a tau number, because it is divible by the number of its divisors (144).

It is not an unprimeable number, because it can be changed into a prime (81061921) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 58354 + ... + 59726.

Almost surely, 2^81061920 is an apocalyptic number.

81061920 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81061920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (141788556).

81061920 is an abundant number, since it is smaller than the sum of its proper divisors (202515192).

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

81061920 is a wasteful number, since it uses less digits than its factorization.

81061920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1435 (or 1424 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 27.

The square root of 81061920 is about 9003.4393428289. The cubic root of 81061920 is about 432.7850949775.

Adding to 81061920 its reverse (2916018), we get a palindrome (83977938).

The spelling of 81061920 in words is "eighty-one million, sixty-one thousand, nine hundred twenty".