21661287363 has 24 divisors (see below), whose sum is σ = 32429025200. Its totient is φ = 13921637184.

The previous prime is 21661287359. The next prime is 21661287391. The reversal of 21661287363 is 36378216612.

21661287363 is a `hidden beast` number, since 2 + 1 + 6 + 6 + 1 + 287 + 363 = 666.

It is not a de Polignac number, because 21661287363 - 2² = 21661287359 is a prime.

It is a super-2 number, since 2×21661287363² (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 (21661287313) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 262093 + ... + 334686.

Almost surely, 2^21661287363 is an apocalyptic number.

21661287363 is a deficient number, since it is larger than the sum of its proper divisors (10767737837).

21661287363 is a wasteful number, since it uses less digits than its factorization.

21661287363 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 596931 (or 596928 counting only the distinct ones).

The product of its digits is 435456, while the sum is 45.

The spelling of 21661287363 in words is "twenty-one billion, six hundred sixty-one million, two hundred eighty-seven thousand, three hundred sixty-three".