2121640236405 has 16 divisors (see below), whose sum is σ = 3771804864960. Its totient is φ = 1131541459344.

The previous prime is 2121640236389. The next prime is 2121640236409. The reversal of 2121640236405 is 5046320461212.

2121640236405 is a `hidden beast` number, since 2 + 1 + 2 + 1 + 6 + 4 + 0 + 2 + 3 + 640 + 5 = 666.

It is not a de Polignac number, because 2121640236405 - 2⁴ = 2121640236389 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 2121640236405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2121640236409) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7857926667 + ... + 7857926936.

It is an arithmetic number, because the mean of its divisors is an integer number (235737804060).

Almost surely, 2^{2121640236405} is an apocalyptic number.

It is an amenable number.

2121640236405 is a deficient number, since it is larger than the sum of its proper divisors (1650164628555).

2121640236405 is a wasteful number, since it uses less digits than its factorization.

2121640236405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15715853617 (or 15715853611 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 36.

Adding to 2121640236405 its reverse (5046320461212), we get a palindrome (7167960697617).

The spelling of 2121640236405 in words is "two trillion, one hundred twenty-one billion, six hundred forty million, two hundred thirty-six thousand, four hundred five".