21555894 has 8 divisors (see below), whose sum is σ = 43111800. Its totient is φ = 7185296.

The previous prime is 21555893. The next prime is 21555917. The reversal of 21555894 is 49855512.

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

21555894 is an admirable number.

It is a super-2 number, since 2×21555894² = 929313132278472, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21555893) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1796319 + ... + 1796330.

It is an arithmetic number, because the mean of its divisors is an integer number (5388975).

Almost surely, 2^21555894 is an apocalyptic number.

21555894 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.

21555894 is a wasteful number, since it uses less digits than its factorization.

21555894 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3592654.

The product of its digits is 72000, while the sum is 39.

The square root of 21555894 is about 4642.8325405942. The cubic root of 21555894 is about 278.3056435177.

The spelling of 21555894 in words is "twenty-one million, five hundred fifty-five thousand, eight hundred ninety-four".