11971921 has 16 divisors (see below), whose sum is σ = 13554688. Its totient is φ = 10497600.

The previous prime is 11971913. The next prime is 11971943. The reversal of 11971921 is 12917911.

It is a happy number.

It is a 8-Lehmer number, since φ(11971921) divides (11971921-1)⁸.

It is a cyclic number.

It is not a de Polignac number, because 11971921 - 2³ = 11971913 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is not an unprimeable number, because it can be changed into a prime (11971901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24340 + ... + 24826.

It is an arithmetic number, because the mean of its divisors is an integer number (847168).

Almost surely, 2^11971921 is an apocalyptic number.

It is an amenable number.

11971921 is a deficient number, since it is larger than the sum of its proper divisors (1582767).

11971921 is a wasteful number, since it uses less digits than its factorization.

11971921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 592.

The product of its digits is 1134, while the sum is 31.

The square root of 11971921 is about 3460.0463869723. The cubic root of 11971921 is about 228.7641399881.

The spelling of 11971921 in words is "eleven million, nine hundred seventy-one thousand, nine hundred twenty-one".