21409621578 has 24 divisors (see below), whose sum is σ = 47173744800. Its totient is φ = 7015581864.

The previous prime is 21409621549. The next prime is 21409621603. The reversal of 21409621578 is 87512690412.

21409621578 is a `hidden beast` number, since 2 + 14 + 0 + 9 + 62 + 1 + 578 = 666.

It is a super-2 number, since 2×21409621578² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10078798 + ... + 10080921.

It is an arithmetic number, because the mean of its divisors is an integer number (1965572700).

Almost surely, 2^21409621578 is an apocalyptic number.

21409621578 is an abundant number, since it is smaller than the sum of its proper divisors (25764123222).

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

21409621578 is a wasteful number, since it uses less digits than its factorization.

21409621578 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20159786 (or 20159783 counting only the distinct ones).

The product of its (nonzero) digits is 241920, while the sum is 45.

The spelling of 21409621578 in words is "twenty-one billion, four hundred nine million, six hundred twenty-one thousand, five hundred seventy-eight".