10921991 has 4 divisors (see below), whose sum is σ = 11044800. Its totient is φ = 10799184.

The previous prime is 10921969. The next prime is 10921997. The reversal of 10921991 is 19912901.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19912901 = 61 ⋅326441.

It is a cyclic number.

It is not a de Polignac number, because 10921991 - 2⁶ = 10921927 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 (10921997) 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, 61271 + ... + 61448.

It is an arithmetic number, because the mean of its divisors is an integer number (2761200).

Almost surely, 2^10921991 is an apocalyptic number.

10921991 is a deficient number, since it is larger than the sum of its proper divisors (122809).

10921991 is an equidigital number, since it uses as much as digits as its factorization.

10921991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 122808.

The product of its (nonzero) digits is 1458, while the sum is 32.

The square root of 10921991 is about 3304.8435666458. The cubic root of 10921991 is about 221.8710326871.

The spelling of 10921991 in words is "ten million, nine hundred twenty-one thousand, nine hundred ninety-one".