21405903976 has 8 divisors (see below), whose sum is σ = 40136069970. Its totient is φ = 10702951984.

The previous prime is 21405903941. The next prime is 21405903983. The reversal of 21405903976 is 67930950412.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 20513687076 + 892216900 = 143226^2 + 29870^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1337868991 + ... + 1337869006.

Almost surely, 2^21405903976 is an apocalyptic number.

It is an amenable number.

21405903976 is a deficient number, since it is larger than the sum of its proper divisors (18730165994).

21405903976 is a wasteful number, since it uses less digits than its factorization.

21405903976 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2675738003 (or 2675737999 counting only the distinct ones).

The product of its (nonzero) digits is 408240, while the sum is 46.

The spelling of 21405903976 in words is "twenty-one billion, four hundred five million, nine hundred three thousand, nine hundred seventy-six".