21150505 has 4 divisors (see below), whose sum is σ = 25380612. Its totient is φ = 16920400.

The previous prime is 21150491. The next prime is 21150523. The reversal of 21150505 is 50505112.

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 11397376 + 9753129 = 3376^2 + 3123^2 .

It is not a de Polignac number, because 21150505 - 2⁷ = 21150377 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2115046 + ... + 2115055.

It is an arithmetic number, because the mean of its divisors is an integer number (6345153).

Almost surely, 2^21150505 is an apocalyptic number.

It is an amenable number.

21150505 is a deficient number, since it is larger than the sum of its proper divisors (4230107).

21150505 is an equidigital number, since it uses as much as digits as its factorization.

21150505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4230106.

The product of its (nonzero) digits is 250, while the sum is 19.

The square root of 21150505 is about 4598.9678189785. The cubic root of 21150505 is about 276.5499475401.

Adding to 21150505 its reverse (50505112), we get a palindrome (71655617).

The spelling of 21150505 in words is "twenty-one million, one hundred fifty thousand, five hundred five".