21393742756 has 9 divisors (see below), whose sum is σ = 37439561761. Its totient is φ = 10696725112.

The previous prime is 21393742691. The next prime is 21393742757. The reversal of 21393742756 is 65724739312.

The square root of 21393742756 is 146266.

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., 16463456100 + 4930286656 = 128310^2 + 70216^2 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21393742757) 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 2 ways as a sum of consecutive naturals, for example, 255966 + ... + 329098.

Almost surely, 2^21393742756 is an apocalyptic number.

21393742756 is the 146266-th square number.

It is an amenable number.

21393742756 is a deficient number, since it is larger than the sum of its proper divisors (16045819005).

21393742756 is an frugal number, since it uses more digits than its factorization.

21393742756 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 146270 (or 73135 counting only the distinct ones).

The product of its digits is 1905120, while the sum is 49.

Multiplying 21393742756 by its sum of digits (49), we get a square (1048293395044 = 1023862²).

The spelling of 21393742756 in words is "twenty-one billion, three hundred ninety-three million, seven hundred forty-two thousand, seven hundred fifty-six".