11721999 has 16 divisors (see below), whose sum is σ = 16231424. Its totient is φ = 7516800.

The previous prime is 11721991. The next prime is 11722001. The reversal of 11721999 is 99912711.

It is not a de Polignac number, because 11721999 - 2³ = 11721991 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 (11721991) 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, 22152 + ... + 22674.

It is an arithmetic number, because the mean of its divisors is an integer number (1014464).

Almost surely, 2^11721999 is an apocalyptic number.

11721999 is a deficient number, since it is larger than the sum of its proper divisors (4509425).

11721999 is a wasteful number, since it uses less digits than its factorization.

11721999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 798.

The product of its digits is 10206, while the sum is 39.

The square root of 11721999 is about 3423.7404983439. The cubic root of 11721999 is about 227.1610635415.

It can be divided in two parts, 11721 and 999, that added together give a triangular number (12720 = T₁₅₉).

The spelling of 11721999 in words is "eleven million, seven hundred twenty-one thousand, nine hundred ninety-nine".