21371281 has 2 divisors, whose sum is σ = 21371282. Its totient is φ = 21371280.

The previous prime is 21371269. The next prime is 21371293. The reversal of 21371281 is 18217312.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (21371269) and next prime (21371293).

It can be written as a sum of positive squares in only one way, i.e., 15872256 + 5499025 = 3984^2 + 2345^2 .

It is a cyclic number.

It is not a de Polignac number, because 21371281 - 2⁷ = 21371153 is a prime.

It is a super-2 number, since 2×21371281² = 913463303161922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21371201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10685640 + 10685641.

It is an arithmetic number, because the mean of its divisors is an integer number (10685641).

Almost surely, 2^21371281 is an apocalyptic number.

It is an amenable number.

21371281 is a deficient number, since it is larger than the sum of its proper divisors (1).

21371281 is an equidigital number, since it uses as much as digits as its factorization.

21371281 is an evil number, because the sum of its binary digits is even.

The product of its digits is 672, while the sum is 25.

The square root of 21371281 is about 4622.9082837539. The cubic root of 21371281 is about 277.5088588466.

Adding to 21371281 its reverse (18217312), we get a palindrome (39588593).

The spelling of 21371281 in words is "twenty-one million, three hundred seventy-one thousand, two hundred eighty-one".