43720821 has 12 divisors (see below), whose sum is σ = 66867372. Its totient is φ = 27432576.

The previous prime is 43720793. The next prime is 43720823. The reversal of 43720821 is 12802734.

43720821 is a `hidden beast` number, since 437 + 208 + 21 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 21958596 + 21762225 = 4686^2 + 4665^2 .

It is not a de Polignac number, because 43720821 - 2⁷ = 43720693 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (43720823) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 142726 + ... + 143031.

It is an arithmetic number, because the mean of its divisors is an integer number (5572281).

Almost surely, 2^43720821 is an apocalyptic number.

It is an amenable number.

43720821 is a deficient number, since it is larger than the sum of its proper divisors (23146551).

43720821 is a wasteful number, since it uses less digits than its factorization.

43720821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 285780 (or 285777 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 43720821 is about 6612.1721846909. The cubic root of 43720821 is about 352.2865827510.

The spelling of 43720821 in words is "forty-three million, seven hundred twenty thousand, eight hundred twenty-one".