21250640261 has 4 divisors (see below), whose sum is σ = 21296145312. Its totient is φ = 21205135212.

The previous prime is 21250640251. The next prime is 21250640287. The reversal of 21250640261 is 16204605212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21250640261 - 2³⁴ = 4070771077 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 (21250640251) 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, 22751825 + ... + 22752758.

It is an arithmetic number, because the mean of its divisors is an integer number (5324036328).

Almost surely, 2^21250640261 is an apocalyptic number.

It is an amenable number.

21250640261 is a deficient number, since it is larger than the sum of its proper divisors (45505051).

21250640261 is an equidigital number, since it uses as much as digits as its factorization.

21250640261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45505050.

The product of its (nonzero) digits is 5760, while the sum is 29.

The spelling of 21250640261 in words is "twenty-one billion, two hundred fifty million, six hundred forty thousand, two hundred sixty-one".