21002420551 has 32 divisors (see below), whose sum is σ = 25664905728. Its totient is φ = 16776913920.

The previous prime is 21002420539. The next prime is 21002420573. The reversal of 21002420551 is 15502420012.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21002420551 is a prime.

It is a super-2 number, since 2×21002420551² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002420501) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 8775411 + ... + 8777803.

It is an arithmetic number, because the mean of its divisors is an integer number (802028304).

Almost surely, 2^21002420551 is an apocalyptic number.

21002420551 is a deficient number, since it is larger than the sum of its proper divisors (4662485177).

21002420551 is a wasteful number, since it uses less digits than its factorization.

21002420551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3111.

The product of its (nonzero) digits is 800, while the sum is 22.

Adding to 21002420551 its reverse (15502420012), we get a palindrome (36504840563).

The spelling of 21002420551 in words is "twenty-one billion, two million, four hundred twenty thousand, five hundred fifty-one".