21242455 has 24 divisors (see below), whose sum is σ = 28829088. Its totient is φ = 14990976.

The previous prime is 21242443. The next prime is 21242461. The reversal of 21242455 is 55424212.

It is not a de Polignac number, because 21242455 - 2¹⁷ = 21111383 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 18889 + ... + 19981.

It is an arithmetic number, because the mean of its divisors is an integer number (1201212).

Almost surely, 2^21242455 is an apocalyptic number.

21242455 is a deficient number, since it is larger than the sum of its proper divisors (7586633).

21242455 is a wasteful number, since it uses less digits than its factorization.

21242455 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1147 (or 1134 counting only the distinct ones).

The product of its digits is 3200, while the sum is 25.

The square root of 21242455 is about 4608.9537858390. The cubic root of 21242455 is about 276.9501272148.

Adding to 21242455 its reverse (55424212), we get a palindrome (76666667).

The spelling of 21242455 in words is "twenty-one million, two hundred forty-two thousand, four hundred fifty-five".