1991025077 has 4 divisors (see below), whose sum is σ = 2009632896. Its totient is φ = 1972417260.

The previous prime is 1991025059. The next prime is 1991025109. The reversal of 1991025077 is 7705201991.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1991025077 - 2⁶ = 1991025013 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991025577) 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 3 ways as a sum of consecutive naturals, for example, 9303749 + ... + 9303962.

It is an arithmetic number, because the mean of its divisors is an integer number (502408224).

Almost surely, 2^1991025077 is an apocalyptic number.

It is an amenable number.

1991025077 is a deficient number, since it is larger than the sum of its proper divisors (18607819).

1991025077 is a wasteful number, since it uses less digits than its factorization.

1991025077 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18607818.

The product of its (nonzero) digits is 39690, while the sum is 41.

The square root of 1991025077 is about 44620.9040361129. The cubic root of 1991025077 is about 1258.0336080641.

The spelling of 1991025077 in words is "one billion, nine hundred ninety-one million, twenty-five thousand, seventy-seven".