21144036781 has 16 divisors (see below), whose sum is σ = 25751752704. Its totient is φ = 16966637424.

The previous prime is 21144036737. The next prime is 21144036811. The reversal of 21144036781 is 18763044112.

It is not a de Polignac number, because 21144036781 - 2²⁹ = 20607165869 is a prime.

It is a super-2 number, since 2×21144036781² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21144036781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21144036181) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1389555 + ... + 1404688.

It is an arithmetic number, because the mean of its divisors is an integer number (1609484544).

Almost surely, 2^21144036781 is an apocalyptic number.

It is an amenable number.

21144036781 is a deficient number, since it is larger than the sum of its proper divisors (4607715923).

21144036781 is a wasteful number, since it uses less digits than its factorization.

21144036781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2794320.

The product of its (nonzero) digits is 32256, while the sum is 37.

The spelling of 21144036781 in words is "twenty-one billion, one hundred forty-four million, thirty-six thousand, seven hundred eighty-one".