21124587649 has 27 divisors (see below), whose sum is σ = 23672806857. Its totient is φ = 18836452800.

The previous prime is 21124587647. The next prime is 21124587661. The reversal of 21124587649 is 94678542112.

The square root of 21124587649 is 145343.

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

It can be written as a sum of positive squares in 4 ways, for example, as 6979767025 + 14144820624 = 83545^2 + 118932^2 .

It is not a de Polignac number, because 21124587649 - 2¹ = 21124587647 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21124587643) 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, 116710339 + ... + 116710519.

Almost surely, 2^21124587649 is an apocalyptic number.

21124587649 is the 145343-rd square number.

21124587649 is the 72672-nd centered octagonal number.

It is an amenable number.

21124587649 is a deficient number, since it is larger than the sum of its proper divisors (2548219208).

21124587649 is an frugal number, since it uses more digits than its factorization.

21124587649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 530 (or 265 counting only the distinct ones).

The product of its digits is 967680, while the sum is 49.

Multiplying 21124587649 by its sum of digits (49), we get a square (1035104794801 = 1017401²).

The spelling of 21124587649 in words is "twenty-one billion, one hundred twenty-four million, five hundred eighty-seven thousand, six hundred forty-nine".