21421505 has 8 divisors (see below), whose sum is σ = 29378112. Its totient is φ = 14689008.

The previous prime is 21421489. The next prime is 21421537. The reversal of 21421505 is 50512412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21421505 - 2⁴ = 21421489 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 305987 + ... + 306056.

It is an arithmetic number, because the mean of its divisors is an integer number (3672264).

Almost surely, 2^21421505 is an apocalyptic number.

It is an amenable number.

21421505 is a deficient number, since it is larger than the sum of its proper divisors (7956607).

21421505 is an equidigital number, since it uses as much as digits as its factorization.

21421505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 612055.

The product of its (nonzero) digits is 400, while the sum is 20.

The square root of 21421505 is about 4628.3371744072. The cubic root of 21421505 is about 277.7260771631.

Adding to 21421505 its reverse (50512412), we get a palindrome (71933917).

The spelling of 21421505 in words is "twenty-one million, four hundred twenty-one thousand, five hundred five".