21436405 has 8 divisors (see below), whose sum is σ = 27236952. Its totient is φ = 16140288.

The previous prime is 21436397. The next prime is 21436409. The reversal of 21436405 is 50463412.

It can be written as a sum of positive squares in 4 ways, for example, as 9284209 + 12152196 = 3047^2 + 3486^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21436405 - 2³ = 21436397 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 21436405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21436409) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 126012 + ... + 126181.

It is an arithmetic number, because the mean of its divisors is an integer number (3404619).

Almost surely, 2^21436405 is an apocalyptic number.

It is an amenable number.

21436405 is a deficient number, since it is larger than the sum of its proper divisors (5800547).

21436405 is a wasteful number, since it uses less digits than its factorization.

21436405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 252215.

The product of its (nonzero) digits is 2880, while the sum is 25.

The square root of 21436405 is about 4629.9465439679. The cubic root of 21436405 is about 277.7904542067.

Adding to 21436405 its reverse (50463412), we get a palindrome (71899817).

The spelling of 21436405 in words is "twenty-one million, four hundred thirty-six thousand, four hundred five".