21511151 has 2 divisors, whose sum is σ = 21511152. Its totient is φ = 21511150.

The previous prime is 21511109. The next prime is 21511153. The reversal of 21511151 is 15111512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21511151 - 2¹⁰ = 21510127 is a prime.

Together with 21511153, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21511153) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10755575 + 10755576.

It is an arithmetic number, because the mean of its divisors is an integer number (10755576).

Almost surely, 2^21511151 is an apocalyptic number.

21511151 is a deficient number, since it is larger than the sum of its proper divisors (1).

21511151 is an equidigital number, since it uses as much as digits as its factorization.

21511151 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 50, while the sum is 17.

The square root of 21511151 is about 4638.0115351301. The cubic root of 21511151 is about 278.1129529100.

Adding to 21511151 its reverse (15111512), we get a palindrome (36622663).

The spelling of 21511151 in words is "twenty-one million, five hundred eleven thousand, one hundred fifty-one".