81613620 has 144 divisors (see below), whose sum is σ = 276127488. Its totient is φ = 19342080.

The previous prime is 81613619. The next prime is 81613621. The reversal of 81613620 is 2631618.

It is an interprime number because it is at equal distance from previous prime (81613619) and next prime (81613621).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81613621) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 92622 + ... + 93498.

It is an arithmetic number, because the mean of its divisors is an integer number (1917552).

Almost surely, 2^81613620 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 81613620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (138063744).

81613620 is an abundant number, since it is smaller than the sum of its proper divisors (194513868).

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

81613620 is a wasteful number, since it uses less digits than its factorization.

81613620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 950 (or 945 counting only the distinct ones).

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

The square root of 81613620 is about 9034.0256807251. The cubic root of 81613620 is about 433.7647078426.

It can be divided in two parts, 8161 and 3620, that added together give a triangular number (11781 = T₁₅₃).

The spelling of 81613620 in words is "eighty-one million, six hundred thirteen thousand, six hundred twenty".