21857878 has 16 divisors (see below), whose sum is σ = 37946880. Its totient is φ = 9248616.

The previous prime is 21857873. The next prime is 21857887. The reversal of 21857878 is 87875812.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21857873) 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, 8776 + ... + 10987.

It is an arithmetic number, because the mean of its divisors is an integer number (2371680).

Almost surely, 2^21857878 is an apocalyptic number.

21857878 is a deficient number, since it is larger than the sum of its proper divisors (16089002).

21857878 is a wasteful number, since it uses less digits than its factorization.

21857878 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19851.

The product of its digits is 250880, while the sum is 46.

The square root of 21857878 is about 4675.2409563572. The cubic root of 21857878 is about 279.5992481234.

The spelling of 21857878 in words is "twenty-one million, eight hundred fifty-seven thousand, eight hundred seventy-eight".