1621066138729 has 4 divisors (see below), whose sum is σ = 1621069654084. Its totient is φ = 1621062623376.

The previous prime is 1621066138709. The next prime is 1621066138807. The reversal of 1621066138729 is 9278316601261.

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 684094410000 + 936971728729 = 827100^2 + 967973^2 .

It is a cyclic number.

It is not a de Polignac number, because 1621066138729 - 2⁹ = 1621066138217 is a prime.

It is a super-2 number, since 2×1621066138729² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1621066138709) 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, 938802 + ... + 2030635.

It is an arithmetic number, because the mean of its divisors is an integer number (405267413521).

Almost surely, 2^{1621066138729} is an apocalyptic number.

It is an amenable number.

1621066138729 is a deficient number, since it is larger than the sum of its proper divisors (3515355).

1621066138729 is an equidigital number, since it uses as much as digits as its factorization.

1621066138729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3515354.

The product of its (nonzero) digits is 1306368, while the sum is 52.

The spelling of 1621066138729 in words is "one trillion, six hundred twenty-one billion, sixty-six million, one hundred thirty-eight thousand, seven hundred twenty-nine".