21007282121 has 4 divisors (see below), whose sum is σ = 24008322432. Its totient is φ = 18006241812.

The previous prime is 21007282099. The next prime is 21007282129. The reversal of 21007282121 is 12128270012.

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 a cyclic number.

It is not a de Polignac number, because 21007282121 - 2¹⁸ = 21007019977 is a prime.

It is a super-2 number, since 2×21007282121² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21007282129) 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 3 ways as a sum of consecutive naturals, for example, 1500520145 + ... + 1500520158.

It is an arithmetic number, because the mean of its divisors is an integer number (6002080608).

Almost surely, 2^21007282121 is an apocalyptic number.

It is an amenable number.

21007282121 is a deficient number, since it is larger than the sum of its proper divisors (3001040311).

21007282121 is an equidigital number, since it uses as much as digits as its factorization.

21007282121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3001040310.

The product of its (nonzero) digits is 896, while the sum is 26.

The spelling of 21007282121 in words is "twenty-one billion, seven million, two hundred eighty-two thousand, one hundred twenty-one".