21661151 has 2 divisors, whose sum is σ = 21661152. Its totient is φ = 21661150.

The previous prime is 21661141. The next prime is 21661181. The reversal of 21661151 is 15116612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21661151 - 2¹⁰ = 21660127 is a 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 (21661141) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830575 + 10830576.

It is an arithmetic number, because the mean of its divisors is an integer number (10830576).

Almost surely, 2^21661151 is an apocalyptic number.

21661151 is a deficient number, since it is larger than the sum of its proper divisors (1).

21661151 is an equidigital number, since it uses as much as digits as its factorization.

21661151 is an evil number, because the sum of its binary digits is even.

The product of its digits is 360, while the sum is 23.

The square root of 21661151 is about 4654.1541659038. The cubic root of 21661151 is about 278.7578951694.

Adding to 21661151 its reverse (15116612), we get a palindrome (36777763).

It can be divided in two parts, 21661 and 151, that added together give a palindrome (21812).

The spelling of 21661151 in words is "twenty-one million, six hundred sixty-one thousand, one hundred fifty-one".