21101577781 has 32 divisors (see below), whose sum is σ = 22707070848. Its totient is φ = 19577376000.

The previous prime is 21101577727. The next prime is 21101577787. The reversal of 21101577781 is 18777510112.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21101577781 is a prime.

It is a super-2 number, since 2×21101577781² (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 (21101577787) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 21164575 + ... + 21165571.

It is an arithmetic number, because the mean of its divisors is an integer number (709595964).

Almost surely, 2^21101577781 is an apocalyptic number.

It is an amenable number.

21101577781 is a deficient number, since it is larger than the sum of its proper divisors (1605493067).

21101577781 is a wasteful number, since it uses less digits than its factorization.

21101577781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1381.

The product of its (nonzero) digits is 27440, while the sum is 40.

The spelling of 21101577781 in words is "twenty-one billion, one hundred one million, five hundred seventy-seven thousand, seven hundred eighty-one".