21575431771 has 4 divisors (see below), whose sum is σ = 21625259992. Its totient is φ = 21525603552.

The previous prime is 21575431753. The next prime is 21575431777. The reversal of 21575431771 is 17713457512.

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 21575431771 - 2⁷ = 21575431643 is a prime.

It is a super-2 number, since 2×21575431771² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21575431777) 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, 24913461 + ... + 24914326.

It is an arithmetic number, because the mean of its divisors is an integer number (5406314998).

Almost surely, 2^21575431771 is an apocalyptic number.

21575431771 is a deficient number, since it is larger than the sum of its proper divisors (49828221).

21575431771 is an equidigital number, since it uses as much as digits as its factorization.

21575431771 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49828220.

The product of its digits is 205800, while the sum is 43.

The spelling of 21575431771 in words is "twenty-one billion, five hundred seventy-five million, four hundred thirty-one thousand, seven hundred seventy-one".