21071662181 has 4 divisors (see below), whose sum is σ = 21149417664. Its totient is φ = 20993906700.

The previous prime is 21071662177. The next prime is 21071662187. The reversal of 21071662181 is 18126617012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21071662181 - 2² = 21071662177 is a prime.

It is a super-2 number, since 2×21071662181² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21071662187) 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, 38877335 + ... + 38877876.

It is an arithmetic number, because the mean of its divisors is an integer number (5287354416).

Almost surely, 2^21071662181 is an apocalyptic number.

It is an amenable number.

21071662181 is a deficient number, since it is larger than the sum of its proper divisors (77755483).

21071662181 is an equidigital number, since it uses as much as digits as its factorization.

21071662181 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77755482.

The product of its (nonzero) digits is 8064, while the sum is 35.

The spelling of 21071662181 in words is "twenty-one billion, seventy-one million, six hundred sixty-two thousand, one hundred eighty-one".