21392251 has 2 divisors, whose sum is σ = 21392252. Its totient is φ = 21392250.

The previous prime is 21392237. The next prime is 21392281. The reversal of 21392251 is 15229312.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21392251 - 2⁷ = 21392123 is a prime.

It is not a weakly prime, because it can be changed into another prime (21392221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10696125 + 10696126.

It is an arithmetic number, because the mean of its divisors is an integer number (10696126).

Almost surely, 2^21392251 is an apocalyptic number.

21392251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21392251 is an equidigital number, since it uses as much as digits as its factorization.

21392251 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1080, while the sum is 25.

The square root of 21392251 is about 4625.1757804434. The cubic root of 21392251 is about 277.5995952332.

The spelling of 21392251 in words is "twenty-one million, three hundred ninety-two thousand, two hundred fifty-one".