21385501 has 4 divisors (see below), whose sum is σ = 21395104. Its totient is φ = 21375900.

The previous prime is 21385471. The next prime is 21385513. The reversal of 21385501 is 10558312.

It is a happy number.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21385501 - 2⁷ = 21385373 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21385591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 466 + ... + 6556.

It is an arithmetic number, because the mean of its divisors is an integer number (5348776).

Almost surely, 2^21385501 is an apocalyptic number.

It is an amenable number.

21385501 is a deficient number, since it is larger than the sum of its proper divisors (9603).

21385501 is an equidigital number, since it uses as much as digits as its factorization.

21385501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9602.

The product of its (nonzero) digits is 1200, while the sum is 25.

The square root of 21385501 is about 4624.4460208764. The cubic root of 21385501 is about 277.5703947159.

The spelling of 21385501 in words is "twenty-one million, three hundred eighty-five thousand, five hundred one".