43721921 has 2 divisors, whose sum is σ = 43721922. Its totient is φ = 43721920.

The previous prime is 43721897. The next prime is 43721939. The reversal of 43721921 is 12912734.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 28472896 + 15249025 = 5336^2 + 3905^2 .

It is a cyclic number.

It is not a de Polignac number, because 43721921 - 2¹⁴ = 43705537 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (43724921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21860960 + 21860961.

It is an arithmetic number, because the mean of its divisors is an integer number (21860961).

Almost surely, 2^43721921 is an apocalyptic number.

It is an amenable number.

43721921 is a deficient number, since it is larger than the sum of its proper divisors (1).

43721921 is an equidigital number, since it uses as much as digits as its factorization.

43721921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3024, while the sum is 29.

The square root of 43721921 is about 6612.2553640948. The cubic root of 43721921 is about 352.2895371937.

The spelling of 43721921 in words is "forty-three million, seven hundred twenty-one thousand, nine hundred twenty-one".