21457790 has 8 divisors (see below), whose sum is σ = 38624040. Its totient is φ = 8583112.

The previous prime is 21457771. The next prime is 21457819. The reversal of 21457790 is 9775412.

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

It is a Curzon number.

It is a zygodrome in base 9.

It is a self number, because there is not a number n which added to its sum of digits gives 21457790.

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, 1072880 + ... + 1072899.

It is an arithmetic number, because the mean of its divisors is an integer number (4828005).

Almost surely, 2^21457790 is an apocalyptic number.

21457790 is a deficient number, since it is larger than the sum of its proper divisors (17166250).

21457790 is a wasteful number, since it uses less digits than its factorization.

21457790 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2145786.

The product of its (nonzero) digits is 17640, while the sum is 35.

The square root of 21457790 is about 4632.2553901960. The cubic root of 21457790 is about 277.8827982747.

The spelling of 21457790 in words is "twenty-one million, four hundred fifty-seven thousand, seven hundred ninety".