21250933729 has 3 divisors (see below), whose sum is σ = 21251079507. Its totient is φ = 21250787952.

The previous prime is 21250933681. The next prime is 21250933733. The reversal of 21250933729 is 92733905212.

The square root of 21250933729 is 145777.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 1525293025 + 19725640704 = 39055^2 + 140448^2 .

It is not a de Polignac number, because 21250933729 - 2⁹ = 21250933217 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21254933729) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 72889 + ... + 218665.

It is an arithmetic number, because the mean of its divisors is an integer number (7083693169).

Almost surely, 2^21250933729 is an apocalyptic number.

21250933729 is the 145777-th square number.

21250933729 is the 72889-th centered octagonal number.

It is an amenable number.

21250933729 is a deficient number, since it is larger than the sum of its proper divisors (145778).

21250933729 is an frugal number, since it uses more digits than its factorization.

21250933729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 291554 (or 145777 counting only the distinct ones).

The product of its (nonzero) digits is 204120, while the sum is 43.

The spelling of 21250933729 in words is "twenty-one billion, two hundred fifty million, nine hundred thirty-three thousand, seven hundred twenty-nine".