21242525561 has 2 divisors, whose sum is σ = 21242525562. Its totient is φ = 21242525560.

The previous prime is 21242525543. The next prime is 21242525611. The reversal of 21242525561 is 16552524212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12749797225 + 8492728336 = 112915^2 + 92156^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21242525561 is a prime.

It is not a weakly prime, because it can be changed into another prime (21242525461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10621262780 + 10621262781.

It is an arithmetic number, because the mean of its divisors is an integer number (10621262781).

Almost surely, 2^21242525561 is an apocalyptic number.

It is an amenable number.

21242525561 is a deficient number, since it is larger than the sum of its proper divisors (1).

21242525561 is an equidigital number, since it uses as much as digits as its factorization.

21242525561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 48000, while the sum is 35.

The spelling of 21242525561 in words is "twenty-one billion, two hundred forty-two million, five hundred twenty-five thousand, five hundred sixty-one".