21110023421 has 2 divisors, whose sum is σ = 21110023422. Its totient is φ = 21110023420.

The previous prime is 21110023399. The next prime is 21110023423. The reversal of 21110023421 is 12432001112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21107731225 + 2292196 = 145285^2 + 1514^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21110023421 is a prime.

Together with 21110023423, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21110023421.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21110023423) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10555011710 + 10555011711.

It is an arithmetic number, because the mean of its divisors is an integer number (10555011711).

Almost surely, 2^21110023421 is an apocalyptic number.

It is an amenable number.

21110023421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21110023421 is an equidigital number, since it uses as much as digits as its factorization.

21110023421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 96, while the sum is 17.

Adding to 21110023421 its reverse (12432001112), we get a palindrome (33542024533).

The spelling of 21110023421 in words is "twenty-one billion, one hundred ten million, twenty-three thousand, four hundred twenty-one".