21645042744 has 96 divisors (see below), whose sum is σ = 61679491200. Its totient is φ = 6309463680.

The previous prime is 21645042709. The next prime is 21645042761. The reversal of 21645042744 is 44724054612.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 63372 + ... + 217499.

It is an arithmetic number, because the mean of its divisors is an integer number (642494700).

Almost surely, 2^21645042744 is an apocalyptic number.

21645042744 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21645042744 is an abundant number, since it is smaller than the sum of its proper divisors (40034448456).

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

21645042744 is a wasteful number, since it uses less digits than its factorization.

21645042744 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 280925 (or 280908 counting only the distinct ones).

The product of its (nonzero) digits is 215040, while the sum is 39.

The spelling of 21645042744 in words is "twenty-one billion, six hundred forty-five million, forty-two thousand, seven hundred forty-four".