21908461 has 4 divisors (see below), whose sum is σ = 23197212. Its totient is φ = 20619712.

The previous prime is 21908449. The next prime is 21908483. The reversal of 21908461 is 16480912.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 18275625 + 3632836 = 4275^2 + 1906^2 .

It is a cyclic number.

It is not a de Polignac number, because 21908461 - 2¹¹ = 21906413 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 (21908401) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 644350 + ... + 644383.

It is an arithmetic number, because the mean of its divisors is an integer number (5799303).

Almost surely, 2^21908461 is an apocalyptic number.

It is an amenable number.

21908461 is a deficient number, since it is larger than the sum of its proper divisors (1288751).

21908461 is a wasteful number, since it uses less digits than its factorization.

21908461 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1288750.

The product of its (nonzero) digits is 3456, while the sum is 31.

The square root of 21908461 is about 4680.6474979430. The cubic root of 21908461 is about 279.8147626852.

The spelling of 21908461 in words is "twenty-one million, nine hundred eight thousand, four hundred sixty-one".