21405250051 has 4 divisors (see below), whose sum is σ = 21405890104. Its totient is φ = 21404610000.

The previous prime is 21405250049. The next prime is 21405250099. The reversal of 21405250051 is 15005250412.

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

It is a cyclic number.

It is not a de Polignac number, because 21405250051 - 2¹ = 21405250049 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21405249998 and 21405250025.

It is not an unprimeable number, because it can be changed into a prime (21405250751) 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, 266925 + ... + 337726.

It is an arithmetic number, because the mean of its divisors is an integer number (5351472526).

Almost surely, 2^21405250051 is an apocalyptic number.

21405250051 is a deficient number, since it is larger than the sum of its proper divisors (640053).

21405250051 is an equidigital number, since it uses as much as digits as its factorization.

21405250051 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 640052.

The product of its (nonzero) digits is 2000, while the sum is 25.

The spelling of 21405250051 in words is "twenty-one billion, four hundred five million, two hundred fifty thousand, fifty-one".