21002400621 has 6 divisors (see below), whose sum is σ = 30336800910. Its totient is φ = 14001600408.

The previous prime is 21002400563. The next prime is 21002400637. The reversal of 21002400621 is 12600420012.

21002400621 is a `hidden beast` number, since 2 + 1 + 0 + 0 + 2 + 40 + 0 + 621 = 666.

It can be written as a sum of positive squares in only one way, i.e., 17132192100 + 3870208521 = 130890^2 + 62211^2 .

It is not a de Polignac number, because 21002400621 - 2⁹ = 21002400109 is a prime.

It is a super-2 number, since 2×21002400621² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21002400594 and 21002400603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002400821) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1166800026 + ... + 1166800043.

It is an arithmetic number, because the mean of its divisors is an integer number (5056133485).

Almost surely, 2^21002400621 is an apocalyptic number.

It is an amenable number.

21002400621 is a deficient number, since it is larger than the sum of its proper divisors (9334400289).

21002400621 is a wasteful number, since it uses less digits than its factorization.

21002400621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2333600075 (or 2333600072 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

Adding to 21002400621 its reverse (12600420012), we get a palindrome (33602820633).

The spelling of 21002400621 in words is "twenty-one billion, two million, four hundred thousand, six hundred twenty-one".