991620100 has 81 divisors (see below), whose sum is σ = 2231877333. Its totient is φ = 382414560.

The previous prime is 991620073. The next prime is 991620103. The reversal of 991620100 is 1026199.

The square root of 991620100 is 31490.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 356983236 + 634636864 = 18894^2 + 25192^2 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991620103) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 14800267 + ... + 14800333.

Almost surely, 2^991620100 is an apocalyptic number.

991620100 is the 31490-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 991620100

991620100 is an abundant number, since it is smaller than the sum of its proper divisors (1240257233).

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

991620100 is a wasteful number, since it uses less digits than its factorization.

991620100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 242 (or 121 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 28.

The cubic root of 991620100 is about 997.1988609463.

Adding to 991620100 its reverse (1026199), we get a palindrome (992646299).

The spelling of 991620100 in words is "nine hundred ninety-one million, six hundred twenty thousand, one hundred".