21261481 has 2 divisors, whose sum is σ = 21261482. Its totient is φ = 21261480.

The previous prime is 21261463. The next prime is 21261511. The reversal of 21261481 is 18416212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21114025 + 147456 = 4595^2 + 384^2 .

It is a cyclic number.

It is not a de Polignac number, because 21261481 - 2¹⁷ = 21130409 is a prime.

It is a super-2 number, since 2×21261481² = 904101148626722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21211481) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10630740 + 10630741.

It is an arithmetic number, because the mean of its divisors is an integer number (10630741).

Almost surely, 2^21261481 is an apocalyptic number.

It is an amenable number.

21261481 is a deficient number, since it is larger than the sum of its proper divisors (1).

21261481 is an equidigital number, since it uses as much as digits as its factorization.

21261481 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 768, while the sum is 25.

The square root of 21261481 is about 4611.0173497830. The cubic root of 21261481 is about 277.0327868501.

Adding to 21261481 its reverse (18416212), we get a palindrome (39677693).

The spelling of 21261481 in words is "twenty-one million, two hundred sixty-one thousand, four hundred eighty-one".