21355145956 has 27 divisors (see below), whose sum is σ = 38632316457. Its totient is φ = 10328751120.

The previous prime is 21355145951. The next prime is 21355145957. The reversal of 21355145956 is 65954155312.

The square root of 21355145956 is 146134.

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., 3882536100 + 17472609856 = 62310^2 + 132184^2 .

It is a Smith number, since the sum of its digits (46) coincides with the sum of the digits of its prime factors.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21355145951) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 9059130 + ... + 9061486.

Almost surely, 2^21355145956 is an apocalyptic number.

21355145956 is the 146134-th square number.

It is an amenable number.

21355145956 is a deficient number, since it is larger than the sum of its proper divisors (17277170501).

21355145956 is an frugal number, since it uses more digits than its factorization.

21355145956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4780 (or 2390 counting only the distinct ones).

The product of its digits is 810000, while the sum is 46.

The spelling of 21355145956 in words is "twenty-one billion, three hundred fifty-five million, one hundred forty-five thousand, nine hundred fifty-six".