20860991 has 4 divisors (see below), whose sum is σ = 21146832. Its totient is φ = 20575152.

The previous prime is 20860969. The next prime is 20861017. The reversal of 20860991 is 19906802.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19906802 = 2 ⋅9953401.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20860991 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 (20860391) 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, 142811 + ... + 142956.

It is an arithmetic number, because the mean of its divisors is an integer number (5286708).

Almost surely, 2^20860991 is an apocalyptic number.

20860991 is a deficient number, since it is larger than the sum of its proper divisors (285841).

20860991 is an equidigital number, since it uses as much as digits as its factorization.

20860991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 285840.

The product of its (nonzero) digits is 7776, while the sum is 35.

The square root of 20860991 is about 4567.3833865792. The cubic root of 20860991 is about 275.2823150348.

The spelling of 20860991 in words is "twenty million, eight hundred sixty thousand, nine hundred ninety-one".