1991564040 has 128 divisors (see below), whose sum is σ = 6408201600. Its totient is φ = 493608960.

The previous prime is 1991564039. The next prime is 1991564077. The reversal of 1991564040 is 404651991.

1991564040 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×1991564040² = 7932654650842243200, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1991564040.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 112600 + ... + 129080.

It is an arithmetic number, because the mean of its divisors is an integer number (50064075).

Almost surely, 2^1991564040 is an apocalyptic number.

1991564040 is a gapful number since it is divisible by the number (10) 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 1991564040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3204100800).

1991564040 is an abundant number, since it is smaller than the sum of its proper divisors (4416637560).

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

1991564040 is a wasteful number, since it uses less digits than its factorization.

1991564040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16567 (or 16563 counting only the distinct ones).

The product of its (nonzero) digits is 38880, while the sum is 39.

The square root of 1991564040 is about 44626.9429829111. The cubic root of 1991564040 is about 1258.1471128117.

The spelling of 1991564040 in words is "one billion, nine hundred ninety-one million, five hundred sixty-four thousand, forty".