20547215649 has 21 divisors (see below), whose sum is σ = 30812534563. Its totient is φ = 13695563592.

The previous prime is 20547215629. The next prime is 20547215651. The reversal of 20547215649 is 94651274502.

The square root of 20547215649 is 143343.

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

20547215649 is a `hidden beast` number, since 20 + 5 + 47 + 21 + 564 + 9 = 666.

It can be written as a sum of positive squares in only one way, i.e., 69605649 + 20477610000 = 8343^2 + 143100^2 .

It is not a de Polignac number, because 20547215649 - 2²¹ = 20545118497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20547215609) by changing a digit.

It is a polite number, since it can be written in 20 ways as a sum of consecutive naturals, for example, 3867607 + ... + 3872915.

Almost surely, 2^20547215649 is an apocalyptic number.

20547215649 is the 143343-rd square number.

20547215649 is the 71672-nd centered octagonal number.

It is an amenable number.

20547215649 is a deficient number, since it is larger than the sum of its proper divisors (10265318914).

20547215649 is an frugal number, since it uses more digits than its factorization.

20547215649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10636 (or 5312 counting only the distinct ones).

The product of its (nonzero) digits is 604800, while the sum is 45.

It can be divided in two parts, 20547 and 215649, that added together give a square (236196 = 486²).

The spelling of 20547215649 in words is "twenty billion, five hundred forty-seven million, two hundred fifteen thousand, six hundred forty-nine".