81315152820 has 72 divisors (see below), whose sum is σ = 269079239520. Its totient is φ = 19712763840.

The previous prime is 81315152803. The next prime is 81315152837. The reversal of 81315152820 is 2825151318.

81315152820 is a `hidden beast` number, since 8 + 131 + 515 + 2 + 8 + 2 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (81315152803) and next prime (81315152837).

It is a super-2 number, since 2×81315152820² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 20532150 + ... + 20536109.

It is an arithmetic number, because the mean of its divisors is an integer number (3737211660).

Almost surely, 2^81315152820 is an apocalyptic number.

It is an amenable number.

81315152820 is an abundant number, since it is smaller than the sum of its proper divisors (187764086700).

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

81315152820 is a wasteful number, since it uses less digits than its factorization.

81315152820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41068285 (or 41068280 counting only the distinct ones).

The product of its (nonzero) digits is 19200, while the sum is 36.

The spelling of 81315152820 in words is "eighty-one billion, three hundred fifteen million, one hundred fifty-two thousand, eight hundred twenty".