21355137761 has 4 divisors (see below), whose sum is σ = 22479092400. Its totient is φ = 20231183124.

The previous prime is 21355137623. The next prime is 21355137781. The reversal of 21355137761 is 16773155312.

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 a de Polignac number, because none of the positive numbers 2^k-21355137761 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21355137781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 561977291 + ... + 561977328.

It is an arithmetic number, because the mean of its divisors is an integer number (5619773100).

Almost surely, 2^21355137761 is an apocalyptic number.

It is an amenable number.

21355137761 is a deficient number, since it is larger than the sum of its proper divisors (1123954639).

21355137761 is a wasteful number, since it uses less digits than its factorization.

21355137761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1123954638.

The product of its digits is 132300, while the sum is 41.

The spelling of 21355137761 in words is "twenty-one billion, three hundred fifty-five million, one hundred thirty-seven thousand, seven hundred sixty-one".