21405661948 has 24 divisors (see below), whose sum is σ = 41969826864. Its totient is φ = 9466876800.

The previous prime is 21405661909. The next prime is 21405661961. The reversal of 21405661948 is 84916650412.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21405661898 and 21405661907.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6572593 + ... + 6575848.

It is an arithmetic number, because the mean of its divisors is an integer number (1748742786).

Almost surely, 2^21405661948 is an apocalyptic number.

It is an amenable number.

21405661948 is a deficient number, since it is larger than the sum of its proper divisors (20564164916).

21405661948 is a wasteful number, since it uses less digits than its factorization.

21405661948 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13148493 (or 13148491 counting only the distinct ones).

The product of its (nonzero) digits is 414720, while the sum is 46.

The spelling of 21405661948 in words is "twenty-one billion, four hundred five million, six hundred sixty-one thousand, nine hundred forty-eight".