21737281 has 2 divisors, whose sum is σ = 21737282. Its totient is φ = 21737280.

The previous prime is 21737263. The next prime is 21737291. The reversal of 21737281 is 18273712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19228225 + 2509056 = 4385^2 + 1584^2 .

It is a cyclic number.

It is not a de Polignac number, because 21737281 - 2⁵ = 21737249 is a prime.

It is a super-2 number, since 2×21737281² = 945018770545922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21737201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10868640 + 10868641.

It is an arithmetic number, because the mean of its divisors is an integer number (10868641).

Almost surely, 2^21737281 is an apocalyptic number.

It is an amenable number.

21737281 is a deficient number, since it is larger than the sum of its proper divisors (1).

21737281 is an equidigital number, since it uses as much as digits as its factorization.

21737281 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4704, while the sum is 31.

The square root of 21737281 is about 4662.3257071981. The cubic root of 21737281 is about 279.0840862844.

The spelling of 21737281 in words is "twenty-one million, seven hundred thirty-seven thousand, two hundred eighty-one".