21420525 has 24 divisors (see below), whose sum is σ = 40475584. Its totient is φ = 9792000.

The previous prime is 21420499. The next prime is 21420541. The reversal of 21420525 is 52502412.

It is a happy number.

It is not a de Polignac number, because 21420525 - 2⁷ = 21420397 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

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, 19876 + ... + 20925.

Almost surely, 2^21420525 is an apocalyptic number.

21420525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21420525 is a deficient number, since it is larger than the sum of its proper divisors (19055059).

21420525 is a wasteful number, since it uses less digits than its factorization.

21420525 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40821 (or 40816 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 21.

The square root of 21420525 is about 4628.2313036407. The cubic root of 21420525 is about 277.7218419222.

Adding to 21420525 its reverse (52502412), we get a palindrome (73922937).

It can be divided in two parts, 21420 and 525, that added together give a triangular number (21945 = T₂₀₉).

The spelling of 21420525 in words is "twenty-one million, four hundred twenty thousand, five hundred twenty-five".