21520151 has 2 divisors, whose sum is σ = 21520152. Its totient is φ = 21520150.

The previous prime is 21520139. The next prime is 21520159. The reversal of 21520151 is 15102512.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21520151 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21520159) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760075 + 10760076.

It is an arithmetic number, because the mean of its divisors is an integer number (10760076).

Almost surely, 2^21520151 is an apocalyptic number.

21520151 is a deficient number, since it is larger than the sum of its proper divisors (1).

21520151 is an equidigital number, since it uses as much as digits as its factorization.

21520151 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 100, while the sum is 17.

The square root of 21520151 is about 4638.9816770494. The cubic root of 21520151 is about 278.1517338440.

Adding to 21520151 its reverse (15102512), we get a palindrome (36622663).

The spelling of 21520151 in words is "twenty-one million, five hundred twenty thousand, one hundred fifty-one".