21776281 has 2 divisors, whose sum is σ = 21776282. Its totient is φ = 21776280.

The previous prime is 21776263. The next prime is 21776317. The reversal of 21776281 is 18267712.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12110400 + 9665881 = 3480^2 + 3109^2 .

It is a cyclic number.

It is not a de Polignac number, because 21776281 - 2²¹ = 19679129 is a prime.

It is a super-2 number, since 2×21776281² = 948412828381922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21776221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10888140 + 10888141.

It is an arithmetic number, because the mean of its divisors is an integer number (10888141).

Almost surely, 2^21776281 is an apocalyptic number.

It is an amenable number.

21776281 is a deficient number, since it is larger than the sum of its proper divisors (1).

21776281 is an equidigital number, since it uses as much as digits as its factorization.

21776281 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9408, while the sum is 34.

The square root of 21776281 is about 4666.5062948634. The cubic root of 21776281 is about 279.2508930482.

The spelling of 21776281 in words is "twenty-one million, seven hundred seventy-six thousand, two hundred eighty-one".