21857642 has 8 divisors (see below), whose sum is σ = 33324132. Its totient is φ = 10749600.

The previous prime is 21857621. The next prime is 21857651. The reversal of 21857642 is 24675812.

It can be written as a sum of positive squares in 2 ways, for example, as 21799561 + 58081 = 4669^2 + 241^2 .

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

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 89459 + ... + 89702.

Almost surely, 2^21857642 is an apocalyptic number.

21857642 is a deficient number, since it is larger than the sum of its proper divisors (11466490).

21857642 is a wasteful number, since it uses less digits than its factorization.

21857642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 179224.

The product of its digits is 26880, while the sum is 35.

The square root of 21857642 is about 4675.2157169483. The cubic root of 21857642 is about 279.5982418400.

The spelling of 21857642 in words is "twenty-one million, eight hundred fifty-seven thousand, six hundred forty-two".