81211004 has 48 divisors (see below), whose sum is σ = 170784768. Its totient is φ = 33058368.

The previous prime is 81211003. The next prime is 81211027. The reversal of 81211004 is 40011218.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81211003) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 43637 + ... + 45459.

It is an arithmetic number, because the mean of its divisors is an integer number (3558016).

Almost surely, 2^81211004 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 81211004, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (85392384).

81211004 is an abundant number, since it is smaller than the sum of its proper divisors (89573764).

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

81211004 is a wasteful number, since it uses less digits than its factorization.

81211004 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1914 (or 1912 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 17.

The square root of 81211004 is about 9011.7148201660. The cubic root of 81211004 is about 433.0502495611.

The spelling of 81211004 in words is "eighty-one million, two hundred eleven thousand, four".