991111002021 has 48 divisors (see below), whose sum is σ = 1693153238400. Its totient is φ = 546620989824.

The previous prime is 991111002019. The next prime is 991111002023. The reversal of 991111002021 is 120200111199.

It is an interprime number because it is at equal distance from previous prime (991111002019) and next prime (991111002023).

It is not a de Polignac number, because 991111002021 - 2¹ = 991111002019 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991111002023) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 4998250 + ... + 5192756.

It is an arithmetic number, because the mean of its divisors is an integer number (35274025800).

Almost surely, 2^991111002021 is an apocalyptic number.

It is an amenable number.

991111002021 is a deficient number, since it is larger than the sum of its proper divisors (702042236379).

991111002021 is a wasteful number, since it uses less digits than its factorization.

991111002021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 197338 (or 197335 counting only the distinct ones).

The product of its (nonzero) digits is 324, while the sum is 27.

The spelling of 991111002021 in words is "nine hundred ninety-one billion, one hundred eleven million, two thousand, twenty-one".