21250405 has 8 divisors (see below), whose sum is σ = 27818784. Its totient is φ = 15454800.

The previous prime is 21250399. The next prime is 21250429. The reversal of 21250405 is 50405212.

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

It is not a de Polignac number, because 21250405 - 2¹⁷ = 21119333 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 193131 + ... + 193240.

It is an arithmetic number, because the mean of its divisors is an integer number (3477348).

Almost surely, 2^21250405 is an apocalyptic number.

It is an amenable number.

21250405 is a deficient number, since it is larger than the sum of its proper divisors (6568379).

21250405 is a wasteful number, since it uses less digits than its factorization.

21250405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 386387.

The product of its (nonzero) digits is 400, while the sum is 19.

The square root of 21250405 is about 4609.8161568548. The cubic root of 21250405 is about 276.9846724827.

Adding to 21250405 its reverse (50405212), we get a palindrome (71655617).

The spelling of 21250405 in words is "twenty-one million, two hundred fifty thousand, four hundred five".