20401906821409 has 15 divisors (see below), whose sum is σ = 20919739848085. Its totient is φ = 19896891708880.

The previous prime is 20401906821343. The next prime is 20401906821421. The reversal of 20401906821409 is 90412860910402.

The square root of 20401906821409 is 4516847.

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

It can be written as a sum of positive squares in 2 ways, for example, as 16659074891809 + 3742831929600 = 4081553^2 + 1934640^2 .

It is not a de Polignac number, because 20401906821409 - 2⁷ = 20401906821281 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20401906821809) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 7592818464 + ... + 7592821150.

Almost surely, 2^{20401906821409} is an apocalyptic number.

20401906821409 is the 4516847-th square number.

20401906821409 is the 2258424-th centered octagonal number.

It is an amenable number.

20401906821409 is a deficient number, since it is larger than the sum of its proper divisors (517833026676).

20401906821409 is an frugal number, since it uses more digits than its factorization.

20401906821409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5538 (or 2728 counting only the distinct ones).

The product of its (nonzero) digits is 248832, while the sum is 46.

The spelling of 20401906821409 in words is "twenty trillion, four hundred one billion, nine hundred six million, eight hundred twenty-one thousand, four hundred nine".