21401020 has 24 divisors (see below), whose sum is σ = 45116064. Its totient is φ = 8527296.

The previous prime is 21400997. The next prime is 21401047. The reversal of 21401020 is 2010412.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a junction number, because it is equal to n+sod(n) for n = 21400988 and 21401006.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3609 + ... + 7471.

It is an arithmetic number, because the mean of its divisors is an integer number (1879836).

Almost surely, 2^21401020 is an apocalyptic number.

21401020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21401020 is an abundant number, since it is smaller than the sum of its proper divisors (23715044).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21401020 is a wasteful number, since it uses less digits than its factorization.

21401020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4149 (or 4147 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 10.

The square root of 21401020 is about 4626.1236472883. The cubic root of 21401020 is about 277.6375207778.

Adding to 21401020 its reverse (2010412), we get a palindrome (23411432).

It can be divided in two parts, 2140 and 1020, that added together give a triangular number (3160 = T₇₉).

The spelling of 21401020 in words is "twenty-one million, four hundred one thousand, twenty".