21012404 has 48 divisors (see below), whose sum is σ = 44728320. Its totient is φ = 8436960.

The previous prime is 21012401. The next prime is 21012413. The reversal of 21012404 is 40421012.

It is a super-2 number, since 2×21012404² = 883042243718432, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (14).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012401) 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, 67409 + ... + 67719.

It is an arithmetic number, because the mean of its divisors is an integer number (931840).

Almost surely, 2^21012404 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21012404, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22364160).

21012404 is an abundant number, since it is smaller than the sum of its proper divisors (23715916).

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

21012404 is a wasteful number, since it uses less digits than its factorization.

21012404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 468 (or 466 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 14.

The square root of 21012404 is about 4583.9288825199. The cubic root of 21012404 is about 275.9467270981.

Adding to 21012404 its reverse (40421012), we get a palindrome (61433416).

It can be divided in two parts, 21012 and 404, that multiplied together give a palindrome (8488848).

The spelling of 21012404 in words is "twenty-one million, twelve thousand, four hundred four".