81239400 has 216 divisors, whose sum is σ = 300690390. Its totient is φ = 19641600.

The previous prime is 81239393. The next prime is 81239423. The reversal of 81239400 is 493218.

It can be written as a sum of positive squares in 3 ways, for example, as 61685316 + 19554084 = 7854^2 + 4422^2 .

It is a super-2 number, since 2×81239400² = 13199680224720000, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 53 ways as a sum of consecutive naturals, for example, 217614 + ... + 217986.

Almost surely, 2^81239400 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 81239400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (150345195).

81239400 is an abundant number, since it is smaller than the sum of its proper divisors (219450990).

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

81239400 is a wasteful number, since it uses less digits than its factorization.

81239400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 417 (or 394 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 81239400 is about 9013.2901872735. The cubic root of 81239400 is about 433.1007167036.

The spelling of 81239400 in words is "eighty-one million, two hundred thirty-nine thousand, four hundred".