991021021111001 has 4 divisors (see below), whose sum is σ = 1034108891594112. Its totient is φ = 947933150627892.

The previous prime is 991021021110997. The next prime is 991021021111081. The reversal of 991021021111001 is 100111120120199.

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 991021021111001 - 2² = 991021021110997 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991021021111081) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21543935241521 + ... + 21543935241566.

It is an arithmetic number, because the mean of its divisors is an integer number (258527222898528).

Almost surely, 2^{991021021111001} is an apocalyptic number.

It is an amenable number.

991021021111001 is a deficient number, since it is larger than the sum of its proper divisors (43087870483111).

991021021111001 is a wasteful number, since it uses less digits than its factorization.

991021021111001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43087870483110.

The product of its (nonzero) digits is 324, while the sum is 29.

The spelling of 991021021111001 in words is "nine hundred ninety-one trillion, twenty-one billion, twenty-one million, one hundred eleven thousand, one".