21857428 has 12 divisors (see below), whose sum is σ = 39183732. Its totient is φ = 10662080.

The previous prime is 21857411. The next prime is 21857431. The reversal of 21857428 is 82475812.

It can be written as a sum of positive squares in 2 ways, for example, as 4318084 + 17539344 = 2078^2 + 4188^2 .

It is a congruent number.

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, 66475 + ... + 66802.

It is an arithmetic number, because the mean of its divisors is an integer number (3265311).

Almost surely, 2^21857428 is an apocalyptic number.

It is an amenable number.

21857428 is a deficient number, since it is larger than the sum of its proper divisors (17326304).

21857428 is a wasteful number, since it uses less digits than its factorization.

21857428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133322 (or 133320 counting only the distinct ones).

The product of its digits is 35840, while the sum is 37.

The square root of 21857428 is about 4675.1928302478. The cubic root of 21857428 is about 279.5973293564.

The spelling of 21857428 in words is "twenty-one million, eight hundred fifty-seven thousand, four hundred twenty-eight".