21420555 has 16 divisors (see below), whose sum is σ = 36909600. Its totient is φ = 10545408.

The previous prime is 21420551. The next prime is 21420563. The reversal of 21420555 is 55502412.

It is a happy number.

It is not a de Polignac number, because 21420555 - 2² = 21420551 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21420551) 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, 54730 + ... + 55119.

It is an arithmetic number, because the mean of its divisors is an integer number (2306850).

Almost surely, 2^21420555 is an apocalyptic number.

21420555 is a deficient number, since it is larger than the sum of its proper divisors (15489045).

21420555 is a wasteful number, since it uses less digits than its factorization.

21420555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 109870.

The product of its (nonzero) digits is 2000, while the sum is 24.

The square root of 21420555 is about 4628.2345446185. The cubic root of 21420555 is about 277.7219715743.

Adding to 21420555 its reverse (55502412), we get a palindrome (76922967).

The spelling of 21420555 in words is "twenty-one million, four hundred twenty thousand, five hundred fifty-five".