21125406 has 8 divisors (see below), whose sum is σ = 42250824. Its totient is φ = 7041800.

The previous prime is 21125393. The next prime is 21125443. The reversal of 21125406 is 60452112.

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

21125406 is an admirable number.

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 3 ways as a sum of consecutive naturals, for example, 1760445 + ... + 1760456.

It is an arithmetic number, because the mean of its divisors is an integer number (5281353).

Almost surely, 2^21125406 is an apocalyptic number.

21125406 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21125406 is a wasteful number, since it uses less digits than its factorization.

21125406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3520906.

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 21125406 is about 4596.2382444778. The cubic root of 21125406 is about 276.4405116253.

Adding to 21125406 its reverse (60452112), we get a palindrome (81577518).

The spelling of 21125406 in words is "twenty-one million, one hundred twenty-five thousand, four hundred six".