21785401 has 4 divisors (see below), whose sum is σ = 23765904. Its totient is φ = 19804900.

The previous prime is 21785377. The next prime is 21785437. The reversal of 21785401 is 10458712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21785401 - 2¹³ = 21777209 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21785401.

It is not an unprimeable number, because it can be changed into a prime (21785441) 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 in 3 ways as a sum of consecutive naturals, for example, 990235 + ... + 990256.

It is an arithmetic number, because the mean of its divisors is an integer number (5941476).

Almost surely, 2^21785401 is an apocalyptic number.

It is an amenable number.

21785401 is a deficient number, since it is larger than the sum of its proper divisors (1980503).

21785401 is a wasteful number, since it uses less digits than its factorization.

21785401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1980502.

The product of its (nonzero) digits is 2240, while the sum is 28.

The square root of 21785401 is about 4667.4833690116. The cubic root of 21785401 is about 279.2898714317.

The spelling of 21785401 in words is "twenty-one million, seven hundred eighty-five thousand, four hundred one".