991221561151 has 16 divisors (see below), whose sum is σ = 1037816784000. Its totient is φ = 945832612608.

The previous prime is 991221561133. The next prime is 991221561167. The reversal of 991221561151 is 151165122199.

It is not a de Polignac number, because 991221561151 - 2⁵ = 991221561119 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 991221561098 and 991221561107.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991221561751) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 702430 + ... + 1573483.

It is an arithmetic number, because the mean of its divisors is an integer number (64863549000).

Almost surely, 2^991221561151 is an apocalyptic number.

991221561151 is a deficient number, since it is larger than the sum of its proper divisors (46595222849).

991221561151 is a wasteful number, since it uses less digits than its factorization.

991221561151 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2276178.

The product of its digits is 48600, while the sum is 43.

The spelling of 991221561151 in words is "nine hundred ninety-one billion, two hundred twenty-one million, five hundred sixty-one thousand, one hundred fifty-one".