21420455 has 32 divisors (see below), whose sum is σ = 30474240. Its totient is φ = 14152320.

The previous prime is 21420449. The next prime is 21420479. The reversal of 21420455 is 55402412.

It is a happy number.

It is not a de Polignac number, because 21420455 - 2⁴ = 21420439 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21420455.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 168602 + ... + 168728.

It is an arithmetic number, because the mean of its divisors is an integer number (952320).

Almost surely, 2^21420455 is an apocalyptic number.

21420455 is a deficient number, since it is larger than the sum of its proper divisors (9053785).

21420455 is a wasteful number, since it uses less digits than its factorization.

21420455 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 279.

The product of its (nonzero) digits is 1600, while the sum is 23.

The square root of 21420455 is about 4628.2237413505. The cubic root of 21420455 is about 277.7215394000.

Adding to 21420455 its reverse (55402412), we get a palindrome (76822867).

The spelling of 21420455 in words is "twenty-one million, four hundred twenty thousand, four hundred fifty-five".