21085570 has 32 divisors (see below), whose sum is σ = 42037056. Its totient is φ = 7550400.

The previous prime is 21085567. The next prime is 21085577. The reversal of 21085570 is 7558012.

It is not an unprimeable number, because it can be changed into a prime (21085577) 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 15 ways as a sum of consecutive naturals, for example, 5940 + ... + 8800.

It is an arithmetic number, because the mean of its divisors is an integer number (1313658).

Almost surely, 2^21085570 is an apocalyptic number.

21085570 is a deficient number, since it is larger than the sum of its proper divisors (20951486).

21085570 is a wasteful number, since it uses less digits than its factorization.

21085570 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2946.

The product of its (nonzero) digits is 2800, while the sum is 28.

The square root of 21085570 is about 4591.9026557626. The cubic root of 21085570 is about 276.2666417771.

It can be divided in two parts, 210855 and 70, that added together give a triangular number (210925 = T₆₄₉).

The spelling of 21085570 in words is "twenty-one million, eighty-five thousand, five hundred seventy".