621621021 has 16 divisors (see below), whose sum is σ = 977788928.
Its totient is φ = 343753200.
The previous prime is 621620999. The next prime is 621621037. The reversal of 621621021 is 120126126.
Adding to 621621021 its reverse (120126126), we get a palindrome (741747147).
621621021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.
It is not a de Polignac number, because 621621021 - 218 = 621358877 is a prime.
It is a Harshad number since it is a multiple of its sum of digits (21).
It is a Duffinian number.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (621621041) 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, 476785 + ... + 478086.
It is an arithmetic number, because the mean of its divisors is an integer number (61111808).
Almost surely, 2621621021 is an apocalyptic number.
It is an amenable number.
621621021 is a deficient number, since it is larger than the sum of its proper divisors (356167907).
621621021 is a wasteful number, since it uses less digits than its factorization.
621621021 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 954912.
The product of its (nonzero) digits is 288, while the sum is 21.
The square root of 621621021 is about 24932.3288322611.
The cubic root of 621621021 is about 853.4443955211.
Note that the first 3 decimals are identical.
The spelling of 621621021 in words is "six hundred twenty-one million, six hundred twenty-one thousand, twenty-one".