21405149 has 2 divisors, whose sum is σ = 21405150. Its totient is φ = 21405148.

The previous prime is 21405127. The next prime is 21405169. The reversal of 21405149 is 94150412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13322500 + 8082649 = 3650^2 + 2843^2 .

It is a cyclic number.

It is not a de Polignac number, because 21405149 - 2¹² = 21401053 is a prime.

It is a plaindrome in base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21405169) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10702574 + 10702575.

It is an arithmetic number, because the mean of its divisors is an integer number (10702575).

Almost surely, 2^21405149 is an apocalyptic number.

It is an amenable number.

21405149 is a deficient number, since it is larger than the sum of its proper divisors (1).

21405149 is an equidigital number, since it uses as much as digits as its factorization.

21405149 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 21405149 is about 4626.5698957219. The cubic root of 21405149 is about 277.6553749363.

The spelling of 21405149 in words is "twenty-one million, four hundred five thousand, one hundred forty-nine".