43405138921 has 9 divisors (see below), whose sum is σ = 43716309399. Its totient is φ = 43096172184.

The previous prime is 43405138897. The next prime is 43405138927. The reversal of 43405138921 is 12983150434.

It is a happy number.

The square root of 43405138921 is 208339.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 12722712025 + 30682426896 = 112795^2 + 175164^2 .

It is not a de Polignac number, because 43405138921 - 2¹⁵ = 43405106153 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (43405138927) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 32708560 + ... + 32709886.

It is an arithmetic number, because the mean of its divisors is an integer number (4857367711).

Almost surely, 2^43405138921 is an apocalyptic number.

43405138921 is the 208339-th square number.

43405138921 is the 104170-th centered octagonal number.

It is an amenable number.

43405138921 is a deficient number, since it is larger than the sum of its proper divisors (311170478).

43405138921 is an frugal number, since it uses more digits than its factorization.

43405138921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2968 (or 1484 counting only the distinct ones).

The product of its (nonzero) digits is 103680, while the sum is 40.

It can be divided in two parts, 4340513 and 8921, that added together give a palindrome (4349434).

The spelling of 43405138921 in words is "forty-three billion, four hundred five million, one hundred thirty-eight thousand, nine hundred twenty-one".