21660400120651 has 4 divisors (see below), whose sum is σ = 21660730440712. Its totient is φ = 21660069800592.

The previous prime is 21660400120591. The next prime is 21660400120657. The reversal of 21660400120651 is 15602100406612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21660400120651 - 2³¹ = 21658252637003 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21660400120657) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 165061650 + ... + 165192823.

It is an arithmetic number, because the mean of its divisors is an integer number (5415182610178).

Almost surely, 2^{21660400120651} is an apocalyptic number.

21660400120651 is a deficient number, since it is larger than the sum of its proper divisors (330320061).

21660400120651 is an equidigital number, since it uses as much as digits as its factorization.

21660400120651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 330320060.

The product of its (nonzero) digits is 17280, while the sum is 34.

The spelling of 21660400120651 in words is "twenty-one trillion, six hundred sixty billion, four hundred million, one hundred twenty thousand, six hundred fifty-one".