21500461 has 4 divisors (see below), whose sum is σ = 22765212. Its totient is φ = 20235712.

The previous prime is 21500459. The next prime is 21500477. The reversal of 21500461 is 16400512.

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 8497225 + 13003236 = 2915^2 + 3606^2 .

It is not a de Polignac number, because 21500461 - 2¹ = 21500459 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 (21500431) 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, 632350 + ... + 632383.

It is an arithmetic number, because the mean of its divisors is an integer number (5691303).

Almost surely, 2^21500461 is an apocalyptic number.

It is an amenable number.

21500461 is a deficient number, since it is larger than the sum of its proper divisors (1264751).

21500461 is a wasteful number, since it uses less digits than its factorization.

21500461 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1264750.

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 21500461 is about 4636.8589583898. The cubic root of 21500461 is about 278.0668757214.

Adding to 21500461 its reverse (16400512), we get a palindrome (37900973).

The spelling of 21500461 in words is "twenty-one million, five hundred thousand, four hundred sixty-one".