21240331421 has 2 divisors, whose sum is σ = 21240331422. Its totient is φ = 21240331420.

The previous prime is 21240331417. The next prime is 21240331447. The reversal of 21240331421 is 12413304212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14774402500 + 6465928921 = 121550^2 + 80411^2 .

It is a cyclic number.

It is not a de Polignac number, because 21240331421 - 2² = 21240331417 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21240331451) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10620165710 + 10620165711.

It is an arithmetic number, because the mean of its divisors is an integer number (10620165711).

Almost surely, 2^21240331421 is an apocalyptic number.

It is an amenable number.

21240331421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21240331421 is an equidigital number, since it uses as much as digits as its factorization.

21240331421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152, while the sum is 23.

Adding to 21240331421 its reverse (12413304212), we get a palindrome (33653635633).

The spelling of 21240331421 in words is "twenty-one billion, two hundred forty million, three hundred thirty-one thousand, four hundred twenty-one".