21556620425 has 6 divisors (see below), whose sum is σ = 26730209358. Its totient is φ = 17245296320.

The previous prime is 21556620419. The next prime is 21556620451. The reversal of 21556620425 is 52402665512.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 248503696 + 21308116729 = 15764^2 + 145973^2 .

It is not a de Polignac number, because 21556620425 - 2¹² = 21556616329 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 431132384 + ... + 431132433.

It is an arithmetic number, because the mean of its divisors is an integer number (4455034893).

Almost surely, 2^21556620425 is an apocalyptic number.

21556620425 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21556620425 is a deficient number, since it is larger than the sum of its proper divisors (5173588933).

21556620425 is an equidigital number, since it uses as much as digits as its factorization.

21556620425 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 862264827 (or 862264822 counting only the distinct ones).

The product of its (nonzero) digits is 144000, while the sum is 38.

The spelling of 21556620425 in words is "twenty-one billion, five hundred fifty-six million, six hundred twenty thousand, four hundred twenty-five".