21123570 has 32 divisors (see below), whose sum is σ = 54597312. Its totient is φ = 5199552.

The previous prime is 21123533. The next prime is 21123589. The reversal of 21123570 is 7532112.

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, 26692 + ... + 27471.

It is an arithmetic number, because the mean of its divisors is an integer number (1706166).

Almost surely, 2^21123570 is an apocalyptic number.

21123570 is an abundant number, since it is smaller than the sum of its proper divisors (33473742).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21123570 is a wasteful number, since it uses less digits than its factorization.

21123570 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54186.

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 21123570 is about 4596.0385115880. The cubic root of 21123570 is about 276.4325029511.

Adding to 21123570 its reverse (7532112), we get a palindrome (28655682).

The spelling of 21123570 in words is "twenty-one million, one hundred twenty-three thousand, five hundred seventy".