21100421021 has 4 divisors (see below), whose sum is σ = 21101688000. Its totient is φ = 21099154044.

The previous prime is 21100421011. The next prime is 21100421039. The reversal of 21100421021 is 12012400112.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21100421021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21100420987 and 21100421005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21100421011) 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 3 ways as a sum of consecutive naturals, for example, 608171 + ... + 641928.

It is an arithmetic number, because the mean of its divisors is an integer number (5275422000).

Almost surely, 2^21100421021 is an apocalyptic number.

It is an amenable number.

21100421021 is a deficient number, since it is larger than the sum of its proper divisors (1266979).

21100421021 is a wasteful number, since it uses less digits than its factorization.

21100421021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1266978.

The product of its (nonzero) digits is 32, while the sum is 14.

Adding to 21100421021 its reverse (12012400112), we get a palindrome (33112821133).

The spelling of 21100421021 in words is "twenty-one billion, one hundred million, four hundred twenty-one thousand, twenty-one".