21780481 has 2 divisors, whose sum is σ = 21780482. Its totient is φ = 21780480.

The previous prime is 21780469. The next prime is 21780487. The reversal of 21780481 is 18408712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11282881 + 10497600 = 3359^2 + 3240^2 .

It is a cyclic number.

It is not a de Polignac number, because 21780481 - 2⁵ = 21780449 is a prime.

It is a super-2 number, since 2×21780481² = 948778705182722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21780487) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10890240 + 10890241.

It is an arithmetic number, because the mean of its divisors is an integer number (10890241).

Almost surely, 2^21780481 is an apocalyptic number.

It is an amenable number.

21780481 is a deficient number, since it is larger than the sum of its proper divisors (1).

21780481 is an equidigital number, since it uses as much as digits as its factorization.

21780481 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3584, while the sum is 31.

The square root of 21780481 is about 4666.9562886318. The cubic root of 21780481 is about 279.2688449712.

The spelling of 21780481 in words is "twenty-one million, seven hundred eighty thousand, four hundred eighty-one".