21785494 has 4 divisors (see below), whose sum is σ = 32678244. Its totient is φ = 10892746.

The previous prime is 21785471. The next prime is 21785497. The reversal of 21785494 is 49458712.

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

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21785497) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5446372 + ... + 5446375.

It is an arithmetic number, because the mean of its divisors is an integer number (8169561).

Almost surely, 2^21785494 is an apocalyptic number.

21785494 is a deficient number, since it is larger than the sum of its proper divisors (10892750).

21785494 is a wasteful number, since it uses less digits than its factorization.

21785494 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10892749.

The product of its digits is 80640, while the sum is 40.

The square root of 21785494 is about 4667.4933315432. The cubic root of 21785494 is about 279.2902688526.

The spelling of 21785494 in words is "twenty-one million, seven hundred eighty-five thousand, four hundred ninety-four".