21421404 has 18 divisors (see below), whose sum is σ = 54148640. Its totient is φ = 7140456.

The previous prime is 21421399. The next prime is 21421427. The reversal of 21421404 is 40412412.

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 297484 + ... + 297555.

Almost surely, 2^21421404 is an apocalyptic number.

It is an amenable number.

21421404 is an abundant number, since it is smaller than the sum of its proper divisors (32727236).

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

21421404 is a wasteful number, since it uses less digits than its factorization.

21421404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 595049 (or 595044 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 18.

The square root of 21421404 is about 4628.3262633483. The cubic root of 21421404 is about 277.7256406800.

Adding to 21421404 its reverse (40412412), we get a palindrome (61833816).

The spelling of 21421404 in words is "twenty-one million, four hundred twenty-one thousand, four hundred four".