81690021504 has 1536 divisors, whose sum is σ = 332666880000. Its totient is φ = 19752284160.

The previous prime is 81690021487. The next prime is 81690021521. The reversal of 81690021504 is 40512009618.

It is an interprime number because it is at equal distance from previous prime (81690021487) and next prime (81690021521).

It is a super-2 number, since 2×81690021504² (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 polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 2635161969 + ... + 2635161999.

It is an arithmetic number, because the mean of its divisors is an integer number (216580000).

Almost surely, 2^81690021504 is an apocalyptic number.

81690021504 is a gapful number since it is divisible by the number (84) 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 81690021504, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (166333440000).

81690021504 is an abundant number, since it is smaller than the sum of its proper divisors (250976858496).

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

81690021504 is a wasteful number, since it uses less digits than its factorization.

81690021504 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 113 (or 75 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The spelling of 81690021504 in words is "eighty-one billion, six hundred ninety million, twenty-one thousand, five hundred four".