21522251 has 2 divisors, whose sum is σ = 21522252. Its totient is φ = 21522250.

The previous prime is 21522223. The next prime is 21522257. The reversal of 21522251 is 15222512.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21522251 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21522257) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10761125 + 10761126.

It is an arithmetic number, because the mean of its divisors is an integer number (10761126).

Almost surely, 2^21522251 is an apocalyptic number.

21522251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21522251 is an equidigital number, since it uses as much as digits as its factorization.

21522251 is an evil number, because the sum of its binary digits is even.

The product of its digits is 400, while the sum is 20.

The square root of 21522251 is about 4639.2080143059. The cubic root of 21522251 is about 278.1607811727.

Adding to 21522251 its reverse (15222512), we get a palindrome (36744763).

The spelling of 21522251 in words is "twenty-one million, five hundred twenty-two thousand, two hundred fifty-one".