21501561404 has 24 divisors (see below), whose sum is σ = 38000693808. Its totient is φ = 10644333440.

The previous prime is 21501561329. The next prime is 21501561439. The reversal of 21501561404 is 40416510512.

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, 805634 + ... + 831894.

It is an arithmetic number, because the mean of its divisors is an integer number (1583362242).

Almost surely, 2^21501561404 is an apocalyptic number.

It is an amenable number.

21501561404 is a deficient number, since it is larger than the sum of its proper divisors (16499132404).

21501561404 is a wasteful number, since it uses less digits than its factorization.

21501561404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28285 (or 28283 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 29.

The spelling of 21501561404 in words is "twenty-one billion, five hundred one million, five hundred sixty-one thousand, four hundred four".