21461521 has 2 divisors, whose sum is σ = 21461522. Its totient is φ = 21461520.

The previous prime is 21461467. The next prime is 21461527. The reversal of 21461521 is 12516412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13838400 + 7623121 = 3720^2 + 2761^2 .

It is a cyclic number.

It is not a de Polignac number, because 21461521 - 2²¹ = 19364369 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21461492 and 21461501.

It is not a weakly prime, because it can be changed into another prime (21461527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10730760 + 10730761.

It is an arithmetic number, because the mean of its divisors is an integer number (10730761).

Almost surely, 2^21461521 is an apocalyptic number.

It is an amenable number.

21461521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21461521 is an equidigital number, since it uses as much as digits as its factorization.

21461521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 480, while the sum is 22.

The square root of 21461521 is about 4632.6580922835. The cubic root of 21461521 is about 277.8989030807.

Adding to 21461521 its reverse (12516412), we get a palindrome (33977933).

The spelling of 21461521 in words is "twenty-one million, four hundred sixty-one thousand, five hundred twenty-one".