11556721 has 4 divisors (see below), whose sum is σ = 12607344. Its totient is φ = 10506100.

The previous prime is 11556709. The next prime is 11556737. The reversal of 11556721 is 12765511.

11556721 is digitally balanced in base 2 and base 3, because in such bases it contains all the possibile digits an equal number of times.

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 not a de Polignac number, because 11556721 - 2⁷ = 11556593 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 11556721.

It is not an unprimeable number, because it can be changed into a prime (11556781) 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, 525295 + ... + 525316.

It is an arithmetic number, because the mean of its divisors is an integer number (3151836).

Almost surely, 2^11556721 is an apocalyptic number.

11556721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

11556721 is a deficient number, since it is larger than the sum of its proper divisors (1050623).

11556721 is a wasteful number, since it uses less digits than its factorization.

11556721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1050622.

The product of its digits is 2100, while the sum is 28.

The square root of 11556721 is about 3399.5177599183. The cubic root of 11556721 is about 226.0883631285.

The spelling of 11556721 in words is "eleven million, five hundred fifty-six thousand, seven hundred twenty-one".