21571620401 has 4 divisors (see below), whose sum is σ = 21572062500. Its totient is φ = 21571178304.

The previous prime is 21571620353. The next prime is 21571620407. The reversal of 21571620401 is 10402617512.

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 20137029025 + 1434591376 = 141905^2 + 37876^2 .

It is a cyclic number.

It is not a de Polignac number, because 21571620401 - 2⁶ = 21571620337 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21571620407) 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, 137276 + ... + 248973.

It is an arithmetic number, because the mean of its divisors is an integer number (5393015625).

Almost surely, 2^21571620401 is an apocalyptic number.

It is an amenable number.

21571620401 is a deficient number, since it is larger than the sum of its proper divisors (442099).

21571620401 is an equidigital number, since it uses as much as digits as its factorization.

21571620401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 442098.

The product of its (nonzero) digits is 3360, while the sum is 29.

The spelling of 21571620401 in words is "twenty-one billion, five hundred seventy-one million, six hundred twenty thousand, four hundred one".