21785746081 has 4 divisors (see below), whose sum is σ = 23766268464. Its totient is φ = 19805223700.

The previous prime is 21785746061. The next prime is 21785746091. The reversal of 21785746081 is 18064758712.

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 21785746081 - 2⁷ = 21785745953 is a prime.

It is a super-2 number, since 2×21785746081² (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 (21785746061) 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, 990261175 + ... + 990261196.

It is an arithmetic number, because the mean of its divisors is an integer number (5941567116).

Almost surely, 2^21785746081 is an apocalyptic number.

It is an amenable number.

21785746081 is a deficient number, since it is larger than the sum of its proper divisors (1980522383).

21785746081 is a wasteful number, since it uses less digits than its factorization.

21785746081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1980522382.

The product of its (nonzero) digits is 752640, while the sum is 49.

The spelling of 21785746081 in words is "twenty-one billion, seven hundred eighty-five million, seven hundred forty-six thousand, eighty-one".