21534251 has 2 divisors, whose sum is σ = 21534252. Its totient is φ = 21534250.

The previous prime is 21534241. The next prime is 21534299. The reversal of 21534251 is 15243512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21534251 - 2¹⁰ = 21533227 is a prime.

It is a super-2 number, since 2×21534251² = 927447932262002, which contains 22 as substring.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (21534221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10767125 + 10767126.

It is an arithmetic number, because the mean of its divisors is an integer number (10767126).

Almost surely, 2^21534251 is an apocalyptic number.

21534251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21534251 is an equidigital number, since it uses as much as digits as its factorization.

21534251 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1200, while the sum is 23.

The square root of 21534251 is about 4640.5011582802. The cubic root of 21534251 is about 278.2124689074.

Adding to 21534251 its reverse (15243512), we get a palindrome (36777763).

The spelling of 21534251 in words is "twenty-one million, five hundred thirty-four thousand, two hundred fifty-one".