21201251 has 2 divisors, whose sum is σ = 21201252. Its totient is φ = 21201250.

The previous prime is 21201209. The next prime is 21201281. The reversal of 21201251 is 15210212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21201251 - 2²² = 17006947 is a prime.

It is not a weakly prime, because it can be changed into another prime (21201281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10600625 + 10600626.

It is an arithmetic number, because the mean of its divisors is an integer number (10600626).

Almost surely, 2^21201251 is an apocalyptic number.

21201251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21201251 is an equidigital number, since it uses as much as digits as its factorization.

21201251 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 40, while the sum is 14.

The square root of 21201251 is about 4604.4816212034. The cubic root of 21201251 is about 276.7709445470.

Adding to 21201251 its reverse (15210212), we get a palindrome (36411463).

The spelling of 21201251 in words is "twenty-one million, two hundred one thousand, two hundred fifty-one".