991840542 has 128 divisors (see below), whose sum is σ = 2578867200. Its totient is φ = 246758400.

The previous prime is 991840529. The next prime is 991840579. The reversal of 991840542 is 245048199.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a junction number, because it is equal to n+sod(n) for n = 991840494 and 991840503.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 2424834 + ... + 2425242.

It is an arithmetic number, because the mean of its divisors is an integer number (20147400).

Almost surely, 2^991840542 is an apocalyptic number.

It is a pronic number, being equal to 31493×31494.

It is a practical number, because each smaller number is the sum of distinct divisors of 991840542, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1289433600).

991840542 is an abundant number, since it is smaller than the sum of its proper divisors (1587026658).

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

991840542 is a wasteful number, since it uses less digits than its factorization.

991840542 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 642.

The product of its (nonzero) digits is 103680, while the sum is 42.

The square root of 991840542 is about 31493.4999960309. The cubic root of 991840542 is about 997.2727495332.

The spelling of 991840542 in words is "nine hundred ninety-one million, eight hundred forty thousand, five hundred forty-two".