21001642544 has 40 divisors (see below), whose sum is σ = 41717298672. Its totient is φ = 10236308480.

The previous prime is 21001642507. The next prime is 21001642547. The reversal of 21001642544 is 44524610012.

It is not an unprimeable number, because it can be changed into a prime (21001642547) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 829172 + ... + 854124.

Almost surely, 2^21001642544 is an apocalyptic number.

It is an amenable number.

21001642544 is a deficient number, since it is larger than the sum of its proper divisors (20715656128).

21001642544 is a wasteful number, since it uses less digits than its factorization.

21001642544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26285 (or 26279 counting only the distinct ones).

The product of its (nonzero) digits is 7680, while the sum is 29.

The spelling of 21001642544 in words is "twenty-one billion, one million, six hundred forty-two thousand, five hundred forty-four".