1909138229821 has 4 divisors (see below), whose sum is σ = 2021440478652. Its totient is φ = 1796835980992.

The previous prime is 1909138229819. The next prime is 1909138229857. The reversal of 1909138229821 is 1289228319091.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 733225713796 + 1175912516025 = 856286^2 + 1084395^2 .

It is not a de Polignac number, because 1909138229821 - 2¹ = 1909138229819 is a prime.

It is a super-2 number, since 2×1909138229821² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1909138229861) 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, 56151124390 + ... + 56151124423.

It is an arithmetic number, because the mean of its divisors is an integer number (505360119663).

Almost surely, 2^{1909138229821} is an apocalyptic number.

It is an amenable number.

1909138229821 is a deficient number, since it is larger than the sum of its proper divisors (112302248831).

1909138229821 is a wasteful number, since it uses less digits than its factorization.

1909138229821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 112302248830.

The product of its (nonzero) digits is 1119744, while the sum is 55.

The spelling of 1909138229821 in words is "one trillion, nine hundred nine billion, one hundred thirty-eight million, two hundred twenty-nine thousand, eight hundred twenty-one".