21256971 has 8 divisors (see below), whose sum is σ = 29320080. Its totient is φ = 13682592.

The previous prime is 21256931. The next prime is 21256997. The reversal of 21256971 is 17965212.

21256971 = T₂₆₆ + T₂₆₇ + ... + T₅₂₆.

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

It is not a de Polignac number, because 21256971 - 2⁷ = 21256843 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (21256931) by changing a digit.

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, 122080 + ... + 122253.

It is an arithmetic number, because the mean of its divisors is an integer number (3665010).

Almost surely, 2^21256971 is an apocalyptic number.

21256971 is a deficient number, since it is larger than the sum of its proper divisors (8063109).

21256971 is a wasteful number, since it uses less digits than its factorization.

21256971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 244365.

The product of its digits is 7560, while the sum is 33.

The square root of 21256971 is about 4610.5282777573. The cubic root of 21256971 is about 277.0131973364.

The spelling of 21256971 in words is "twenty-one million, two hundred fifty-six thousand, nine hundred seventy-one".