21261278851 has 2 divisors, whose sum is σ = 21261278852. Its totient is φ = 21261278850.

The previous prime is 21261278839. The next prime is 21261278861. The reversal of 21261278851 is 15887216212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21261278851 - 2¹⁷ = 21261147779 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21261278798 and 21261278807.

It is not a weakly prime, because it can be changed into another prime (21261278861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10630639425 + 10630639426.

It is an arithmetic number, because the mean of its divisors is an integer number (10630639426).

Almost surely, 2^21261278851 is an apocalyptic number.

21261278851 is a deficient number, since it is larger than the sum of its proper divisors (1).

21261278851 is an equidigital number, since it uses as much as digits as its factorization.

21261278851 is an evil number, because the sum of its binary digits is even.

The product of its digits is 107520, while the sum is 43.

The spelling of 21261278851 in words is "twenty-one billion, two hundred sixty-one million, two hundred seventy-eight thousand, eight hundred fifty-one".