21004574661 has 30 divisors (see below), whose sum is σ = 35394528390. Its totient is φ = 12002601744.

The previous prime is 21004574653. The next prime is 21004574677. The reversal of 21004574661 is 16647540012.

21004574661 is a `hidden beast` number, since 2 + 100 + 457 + 46 + 61 = 666.

It can be written as a sum of positive squares in only one way, i.e., 20122841025 + 881733636 = 141855^2 + 29694^2 .

It is not a de Polignac number, because 21004574661 - 2³ = 21004574653 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21004574611) by changing a digit.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 464406 + ... + 507623.

It is an arithmetic number, because the mean of its divisors is an integer number (1179817613).

Almost surely, 2^21004574661 is an apocalyptic number.

21004574661 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21004574661 is a deficient number, since it is larger than the sum of its proper divisors (14389953729).

21004574661 is an frugal number, since it uses more digits than its factorization.

21004574661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 972063 (or 972039 counting only the distinct ones).

The product of its (nonzero) digits is 40320, while the sum is 36.

The spelling of 21004574661 in words is "twenty-one billion, four million, five hundred seventy-four thousand, six hundred sixty-one".