21256635035261 has 4 divisors (see below), whose sum is σ = 21989622450300. Its totient is φ = 20523647620224.

The previous prime is 21256635035221. The next prime is 21256635035359. The reversal of 21256635035261 is 16253053665212.

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 11910132623236 + 9346502412025 = 3451106^2 + 3057205^2 .

It is a cyclic number.

It is not a de Polignac number, because 21256635035261 - 2⁶ = 21256635035197 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21256635035221) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 366493707476 + ... + 366493707533.

It is an arithmetic number, because the mean of its divisors is an integer number (5497405612575).

Almost surely, 2^{21256635035261} is an apocalyptic number.

It is an amenable number.

21256635035261 is a deficient number, since it is larger than the sum of its proper divisors (732987415039).

21256635035261 is an equidigital number, since it uses as much as digits as its factorization.

21256635035261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 732987415038.

The product of its (nonzero) digits is 1944000, while the sum is 47.

The spelling of 21256635035261 in words is "twenty-one trillion, two hundred fifty-six billion, six hundred thirty-five million, thirty-five thousand, two hundred sixty-one".