21421559 has 2 divisors, whose sum is σ = 21421560. Its totient is φ = 21421558.

The previous prime is 21421549. The next prime is 21421597. The reversal of 21421559 is 95512412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21421559 - 2¹² = 21417463 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21421549) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10710779 + 10710780.

It is an arithmetic number, because the mean of its divisors is an integer number (10710780).

Almost surely, 2^21421559 is an apocalyptic number.

21421559 is a deficient number, since it is larger than the sum of its proper divisors (1).

21421559 is an equidigital number, since it uses as much as digits as its factorization.

21421559 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3600, while the sum is 29.

The square root of 21421559 is about 4628.3430080321. The cubic root of 21421559 is about 277.7263105298.

The spelling of 21421559 in words is "twenty-one million, four hundred twenty-one thousand, five hundred fifty-nine".