21897557 has 8 divisors (see below), whose sum is σ = 25145760. Its totient is φ = 18858960.

The previous prime is 21897553. The next prime is 21897559. The reversal of 21897557 is 75579812.

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

It is a cyclic number.

It is not a de Polignac number, because 21897557 - 2² = 21897553 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21897553) 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 7 ways as a sum of consecutive naturals, for example, 52178 + ... + 52595.

It is an arithmetic number, because the mean of its divisors is an integer number (3143220).

Almost surely, 2^21897557 is an apocalyptic number.

It is an amenable number.

21897557 is a deficient number, since it is larger than the sum of its proper divisors (3248203).

21897557 is a wasteful number, since it uses less digits than its factorization.

21897557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104803.

The product of its digits is 176400, while the sum is 44.

The square root of 21897557 is about 4679.4825568646. The cubic root of 21897557 is about 279.7683330356.

The spelling of 21897557 in words is "twenty-one million, eight hundred ninety-seven thousand, five hundred fifty-seven".