21425555 has 12 divisors (see below), whose sum is σ = 26175072. Its totient is φ = 16836240.

The previous prime is 21425549. The next prime is 21425587. The reversal of 21425555 is 55552412.

It is not a de Polignac number, because 21425555 - 2⁴ = 21425539 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 16790 + ... + 18020.

It is an arithmetic number, because the mean of its divisors is an integer number (2181256).

Almost surely, 2^21425555 is an apocalyptic number.

21425555 is a deficient number, since it is larger than the sum of its proper divisors (4749517).

21425555 is an equidigital number, since it uses as much as digits as its factorization.

21425555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1354 (or 1295 counting only the distinct ones).

The product of its digits is 10000, while the sum is 29.

The square root of 21425555 is about 4628.7746758727. The cubic root of 21425555 is about 277.7435785749.

Adding to 21425555 its reverse (55552412), we get a palindrome (76977967).

The spelling of 21425555 in words is "twenty-one million, four hundred twenty-five thousand, five hundred fifty-five".