21256005 has 8 divisors (see below), whose sum is σ = 34009632. Its totient is φ = 11336528.

The previous prime is 21255973. The next prime is 21256013. The reversal of 21256005 is 50065212.

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 21256005 - 2⁵ = 21255973 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 708519 + ... + 708548.

It is an arithmetic number, because the mean of its divisors is an integer number (4251204).

Almost surely, 2^21256005 is an apocalyptic number.

It is an amenable number.

21256005 is a deficient number, since it is larger than the sum of its proper divisors (12753627).

21256005 is a wasteful number, since it uses less digits than its factorization.

21256005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1417075.

The product of its (nonzero) digits is 600, while the sum is 21.

The square root of 21256005 is about 4610.4235163377. The cubic root of 21256005 is about 277.0090010846.

The spelling of 21256005 in words is "twenty-one million, two hundred fifty-six thousand, five".