2121662021721 has 32 divisors (see below), whose sum is σ = 3152614791168. Its totient is φ = 1258137675840.

The previous prime is 2121662021719. The next prime is 2121662021737. The reversal of 2121662021721 is 1271202661212.

It is not a de Polignac number, because 2121662021721 - 2¹ = 2121662021719 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (2121662021761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 5286090 + ... + 5673276.

It is an arithmetic number, because the mean of its divisors is an integer number (98519212224).

Almost surely, 2^{2121662021721} is an apocalyptic number.

It is an amenable number.

2121662021721 is a deficient number, since it is larger than the sum of its proper divisors (1030952769447).

2121662021721 is a wasteful number, since it uses less digits than its factorization.

2121662021721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 390781.

The product of its (nonzero) digits is 8064, while the sum is 33.

Adding to 2121662021721 its reverse (1271202661212), we get a palindrome (3392864682933).

The spelling of 2121662021721 in words is "two trillion, one hundred twenty-one billion, six hundred sixty-two million, twenty-one thousand, seven hundred twenty-one".