21256870 has 32 divisors (see below), whose sum is σ = 39885408. Its totient is φ = 8149248.

The previous prime is 21256867. The next prime is 21256909. The reversal of 21256870 is 7865212.

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 15 ways as a sum of consecutive naturals, for example, 26617 + ... + 27403.

It is an arithmetic number, because the mean of its divisors is an integer number (1246419).

Almost surely, 2^21256870 is an apocalyptic number.

21256870 is a deficient number, since it is larger than the sum of its proper divisors (18628538).

21256870 is a wasteful number, since it uses less digits than its factorization.

21256870 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 904.

The product of its (nonzero) digits is 6720, while the sum is 31.

The square root of 21256870 is about 4610.5173245526. The cubic root of 21256870 is about 277.0127586038.

The spelling of 21256870 in words is "twenty-one million, two hundred fifty-six thousand, eight hundred seventy".