21368884761 has 27 divisors (see below), whose sum is σ = 35910699903. Its totient is φ = 12209037120.

The previous prime is 21368884759. The next prime is 21368884783. The reversal of 21368884761 is 16748886312.

The square root of 21368884761 is 146181.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 16739443161 + 4629441600 = 129381^2 + 68040^2 .

It is not a de Polignac number, because 21368884761 - 2¹ = 21368884759 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21368884698 and 21368884707.

It is not an unprimeable number, because it can be changed into a prime (21368882761) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 3066321 + ... + 3073281.

Almost surely, 2^21368884761 is an apocalyptic number.

21368884761 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21368884761 is the 146181-st square number.

21368884761 is the 73091-st centered octagonal number.

It is an amenable number.

21368884761 is a deficient number, since it is larger than the sum of its proper divisors (14541815142).

21368884761 is an frugal number, since it uses more digits than its factorization.

21368884761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13942 (or 6971 counting only the distinct ones).

The product of its digits is 3096576, while the sum is 54.

The spelling of 21368884761 in words is "twenty-one billion, three hundred sixty-eight million, eight hundred eighty-four thousand, seven hundred sixty-one".