21207420663 has 16 divisors (see below), whose sum is σ = 33220016256. Its totient is φ = 11864291040.

The previous prime is 21207420599. The next prime is 21207420671. The reversal of 21207420663 is 36602470212.

It is not a de Polignac number, because 21207420663 - 2⁶ = 21207420599 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21207420263) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24716845 + ... + 24717702.

It is an arithmetic number, because the mean of its divisors is an integer number (2076251016).

Almost surely, 2^21207420663 is an apocalyptic number.

21207420663 is a deficient number, since it is larger than the sum of its proper divisors (12012595593).

21207420663 is a wasteful number, since it uses less digits than its factorization.

21207420663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49434574.

The product of its (nonzero) digits is 24192, while the sum is 33.

Adding to 21207420663 its reverse (36602470212), we get a palindrome (57809890875).

The spelling of 21207420663 in words is "twenty-one billion, two hundred seven million, four hundred twenty thousand, six hundred sixty-three".