21404477 has 4 divisors (see below), whose sum is σ = 22094976. Its totient is φ = 20713980.

The previous prime is 21404459. The next prime is 21404491. The reversal of 21404477 is 77440412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21404477 - 2⁶ = 21404413 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21404417) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 345203 + ... + 345264.

It is an arithmetic number, because the mean of its divisors is an integer number (5523744).

Almost surely, 2^21404477 is an apocalyptic number.

It is an amenable number.

21404477 is a deficient number, since it is larger than the sum of its proper divisors (690499).

21404477 is an equidigital number, since it uses as much as digits as its factorization.

21404477 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 690498.

The product of its (nonzero) digits is 6272, while the sum is 29.

The square root of 21404477 is about 4626.4972711545. The cubic root of 21404477 is about 277.6524693057.

Adding to 21404477 its reverse (77440412), we get a palindrome (98844889).

The spelling of 21404477 in words is "twenty-one million, four hundred four thousand, four hundred seventy-seven".