991224128 has 28 divisors (see below), whose sum is σ = 1973996052. Its totient is φ = 493839360.

The previous prime is 991224121. The next prime is 991224133. The reversal of 991224128 is 821422199.

It can be written as a sum of positive squares in 2 ways, for example, as 852172864 + 139051264 = 29192^2 + 11792^2 .

It is a junction number, because it is equal to n+sod(n) for n = 991224091 and 991224100.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991224121) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9575 + ... + 45542.

It is an arithmetic number, because the mean of its divisors is an integer number (70499859).

Almost surely, 2^991224128 is an apocalyptic number.

It is an amenable number.

991224128 is a deficient number, since it is larger than the sum of its proper divisors (982771924).

991224128 is a wasteful number, since it uses less digits than its factorization.

991224128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55410 (or 55400 counting only the distinct ones).

The product of its digits is 20736, while the sum is 38.

The square root of 991224128 is about 31483.7121064210. The cubic root of 991224128 is about 997.0661100411.

The spelling of 991224128 in words is "nine hundred ninety-one million, two hundred twenty-four thousand, one hundred twenty-eight".