21857641 has 8 divisors (see below), whose sum is σ = 23838080. Its totient is φ = 19919952.

The previous prime is 21857621. The next prime is 21857651. The reversal of 21857641 is 14675812.

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

It is not a de Polignac number, because 21857641 - 2⁵ = 21857609 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21857597 and 21857606.

It is not an unprimeable number, because it can be changed into a prime (21857621) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9615 + ... + 11668.

It is an arithmetic number, because the mean of its divisors is an integer number (2979760).

Almost surely, 2^21857641 is an apocalyptic number.

It is an amenable number.

21857641 is a deficient number, since it is larger than the sum of its proper divisors (1980439).

21857641 is a wasteful number, since it uses less digits than its factorization.

21857641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21375.

The product of its digits is 13440, while the sum is 34.

The square root of 21857641 is about 4675.2156100013. The cubic root of 21857641 is about 279.5982375761.

The spelling of 21857641 in words is "twenty-one million, eight hundred fifty-seven thousand, six hundred forty-one".