21256036061 has 4 divisors (see below), whose sum is σ = 22891115772. Its totient is φ = 19620956352.

The previous prime is 21256036031. The next prime is 21256036093. The reversal of 21256036061 is 16063065212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7589023225 + 13667012836 = 87115^2 + 116906^2 .

It is a cyclic number.

It is not a de Polignac number, because 21256036061 - 2¹⁰ = 21256035037 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21256036001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 817539836 + ... + 817539861.

It is an arithmetic number, because the mean of its divisors is an integer number (5722778943).

Almost surely, 2^21256036061 is an apocalyptic number.

It is an amenable number.

21256036061 is a deficient number, since it is larger than the sum of its proper divisors (1635079711).

21256036061 is a wasteful number, since it uses less digits than its factorization.

21256036061 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1635079710.

The product of its (nonzero) digits is 12960, while the sum is 32.

The spelling of 21256036061 in words is "twenty-one billion, two hundred fifty-six million, thirty-six thousand, sixty-one".