21102421 has 2 divisors, whose sum is σ = 21102422. Its totient is φ = 21102420.

The previous prime is 21102409. The next prime is 21102439. The reversal of 21102421 is 12420112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16200625 + 4901796 = 4025^2 + 2214^2 .

It is a cyclic number.

It is not a de Polignac number, because 21102421 - 2⁹ = 21101909 is a prime.

It is a super-2 number, since 2×21102421² = 890624344122482, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21102451) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10551210 + 10551211.

It is an arithmetic number, because the mean of its divisors is an integer number (10551211).

Almost surely, 2^21102421 is an apocalyptic number.

It is an amenable number.

21102421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21102421 is an equidigital number, since it uses as much as digits as its factorization.

21102421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 21102421 is about 4593.7371496419. The cubic root of 21102421 is about 276.3402170481.

Adding to 21102421 its reverse (12420112), we get a palindrome (33522533).

The spelling of 21102421 in words is "twenty-one million, one hundred two thousand, four hundred twenty-one".