21621752121 has 4 divisors (see below), whose sum is σ = 28829002832. Its totient is φ = 14414501412.

The previous prime is 21621752099. The next prime is 21621752137. The reversal of 21621752121 is 12125712612.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21621752121 - 2¹⁸ = 21621489977 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21621752521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3603625351 + ... + 3603625356.

It is an arithmetic number, because the mean of its divisors is an integer number (7207250708).

Almost surely, 2^21621752121 is an apocalyptic number.

It is an amenable number.

21621752121 is a deficient number, since it is larger than the sum of its proper divisors (7207250711).

21621752121 is an equidigital number, since it uses as much as digits as its factorization.

21621752121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7207250710.

The product of its digits is 3360, while the sum is 30.

The spelling of 21621752121 in words is "twenty-one billion, six hundred twenty-one million, seven hundred fifty-two thousand, one hundred twenty-one".