21116251 has 4 divisors (see below), whose sum is σ = 22740592. Its totient is φ = 19491912.

The previous prime is 21116219. The next prime is 21116257. The reversal of 21116251 is 15261112.

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 21116251 - 2⁵ = 21116219 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21116257) 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, 812151 + ... + 812176.

It is an arithmetic number, because the mean of its divisors is an integer number (5685148).

Almost surely, 2^21116251 is an apocalyptic number.

21116251 is a deficient number, since it is larger than the sum of its proper divisors (1624341).

21116251 is a wasteful number, since it uses less digits than its factorization.

21116251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1624340.

The product of its digits is 120, while the sum is 19.

The square root of 21116251 is about 4595.2422134203. The cubic root of 21116251 is about 276.4005726918.

Adding to 21116251 its reverse (15261112), we get a palindrome (36377363).

The spelling of 21116251 in words is "twenty-one million, one hundred sixteen thousand, two hundred fifty-one".