81438100 has 18 divisors (see below), whose sum is σ = 176720894. Its totient is φ = 32575200.

The previous prime is 81438089. The next prime is 81438107. The reversal of 81438100 is 183418.

It can be written as a sum of positive squares in 3 ways, for example, as 41616 + 81396484 = 204^2 + 9022^2 .

It is a super-2 number, since 2×81438100² = 13264328263220000, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81438107) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 407091 + ... + 407290.

Almost surely, 2^81438100 is an apocalyptic number.

It is an amenable number.

81438100 is an abundant number, since it is smaller than the sum of its proper divisors (95282794).

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

81438100 is a wasteful number, since it uses less digits than its factorization.

81438100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 814395 (or 814388 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 25.

The square root of 81438100 is about 9024.3060675046. The cubic root of 81438100 is about 433.4535301022.

It can be divided in two parts, 81 and 438100, that multiplied together give a triangular number (35486100 = T₈₄₂₄).

The spelling of 81438100 in words is "eighty-one million, four hundred thirty-eight thousand, one hundred".