21857378 has 4 divisors (see below), whose sum is σ = 32786070. Its totient is φ = 10928688.

The previous prime is 21857377. The next prime is 21857389. The reversal of 21857378 is 87375812.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 21836929 + 20449 = 4673^2 + 143^2 .

It is not an unprimeable number, because it can be changed into a prime (21857377) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5464343 + ... + 5464346.

Almost surely, 2^21857378 is an apocalyptic number.

21857378 is a deficient number, since it is larger than the sum of its proper divisors (10928692).

21857378 is a wasteful number, since it uses less digits than its factorization.

21857378 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10928691.

The product of its digits is 94080, while the sum is 41.

The square root of 21857378 is about 4675.1874828717. The cubic root of 21857378 is about 279.5971161584.

The spelling of 21857378 in words is "twenty-one million, eight hundred fifty-seven thousand, three hundred seventy-eight".