21661610345 has 32 divisors (see below), whose sum is σ = 27599153280. Its totient is φ = 16275479040.

The previous prime is 21661610317. The next prime is 21661610351. The reversal of 21661610345 is 54301616612.

It is not a de Polignac number, because 21661610345 - 2⁶ = 21661610281 is a prime.

It is a super-2 number, since 2×21661610345² (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 31 ways as a sum of consecutive naturals, for example, 7075115 + ... + 7078175.

It is an arithmetic number, because the mean of its divisors is an integer number (862473540).

Almost surely, 2^21661610345 is an apocalyptic number.

It is an amenable number.

21661610345 is a deficient number, since it is larger than the sum of its proper divisors (5937542935).

21661610345 is a wasteful number, since it uses less digits than its factorization.

21661610345 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3705.

The product of its (nonzero) digits is 25920, while the sum is 35.

The spelling of 21661610345 in words is "twenty-one billion, six hundred sixty-one million, six hundred ten thousand, three hundred forty-five".