21115151 has 4 divisors (see below), whose sum is σ = 21129552. Its totient is φ = 21100752.

The previous prime is 21115141. The next prime is 21115189. The reversal of 21115151 is 15151112.

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

It is a cyclic number.

It is not a de Polignac number, because 21115151 - 2¹⁰ = 21114127 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 (21115141) 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, 4715 + ... + 8028.

It is an arithmetic number, because the mean of its divisors is an integer number (5282388).

Almost surely, 2^21115151 is an apocalyptic number.

21115151 is a deficient number, since it is larger than the sum of its proper divisors (14401).

21115151 is a wasteful number, since it uses less digits than its factorization.

21115151 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14400.

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

The square root of 21115151 is about 4595.1225228496. The cubic root of 21115151 is about 276.3957731354.

Adding to 21115151 its reverse (15151112), we get a palindrome (36266263).

The spelling of 21115151 in words is "twenty-one million, one hundred fifteen thousand, one hundred fifty-one".