21001532544 has 48 divisors (see below), whose sum is σ = 60434100870. Its totient is φ = 7000510464.

The previous prime is 21001532537. The next prime is 21001532549. The reversal of 21001532544 is 44523510012.

21001532544 is a `hidden beast` number, since 2 + 100 + 15 + 3 + 2 + 544 = 666.

It can be written as a sum of positive squares in only one way, i.e., 20992532544 + 9000000 = 144888^2 + 3000^2 .

It is a tau number, because it is divible by the number of its divisors (48).

It is a super-2 number, since 2×21001532544² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21001532549) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 9114097 + ... + 9116400.

Almost surely, 2^21001532544 is an apocalyptic number.

21001532544 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21001532544 is an abundant number, since it is smaller than the sum of its proper divisors (39432568326).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21001532544 is a wasteful number, since it uses less digits than its factorization.

21001532544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18230517 (or 18230502 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 27.

The spelling of 21001532544 in words is "twenty-one billion, one million, five hundred thirty-two thousand, five hundred forty-four".