99971820 has 240 divisors, whose sum is σ = 348340608. Its totient is φ = 23846400.

The previous prime is 99971813. The next prime is 99971827. The reversal of 99971820 is 2817999.

It is an interprime number because it is at equal distance from previous prime (99971813) and next prime (99971827).

It is a super-2 number, since 2×99971820² = 19988729588224800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (99971827) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 989770 + ... + 989870.

Almost surely, 2^99971820 is an apocalyptic number.

99971820 is a gapful number since it is divisible by the number (90) 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 99971820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (174170304).

99971820 is an abundant number, since it is smaller than the sum of its proper divisors (248368788).

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

99971820 is a wasteful number, since it uses less digits than its factorization.

99971820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 182 (or 171 counting only the distinct ones).

The product of its (nonzero) digits is 81648, while the sum is 45.

The square root of 99971820 is about 9998.5909007220. The cubic root of 99971820 is about 464.1152792740.

The spelling of 99971820 in words is "ninety-nine million, nine hundred seventy-one thousand, eight hundred twenty".