21501661730 has 16 divisors (see below), whose sum is σ = 38869102584. Its totient is φ = 8563751040.

The previous prime is 21501661681. The next prime is 21501661751. The reversal of 21501661730 is 3716610512.

It can be written as a sum of positive squares in 4 ways, for example, as 6938723401 + 14562938329 = 83299^2 + 120677^2 .

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, 4611761 + ... + 4616420.

Almost surely, 2^21501661730 is an apocalyptic number.

21501661730 is a deficient number, since it is larger than the sum of its proper divisors (17367440854).

21501661730 is a wasteful number, since it uses less digits than its factorization.

21501661730 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9228421.

The product of its (nonzero) digits is 7560, while the sum is 32.

The spelling of 21501661730 in words is "twenty-one billion, five hundred one million, six hundred sixty-one thousand, seven hundred thirty".