21220725 has 24 divisors (see below), whose sum is σ = 35216992. Its totient is φ = 11275200.

The previous prime is 21220711. The next prime is 21220733. The reversal of 21220725 is 52702212.

It is a happy number.

It is not a de Polignac number, because 21220725 - 2⁷ = 21220597 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, 38955 + ... + 39495.

Almost surely, 2^21220725 is an apocalyptic number.

21220725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21220725 is a deficient number, since it is larger than the sum of its proper divisors (13996267).

21220725 is a wasteful number, since it uses less digits than its factorization.

21220725 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1077 (or 1072 counting only the distinct ones).

The product of its (nonzero) digits is 560, while the sum is 21.

The square root of 21220725 is about 4606.5958146987. The cubic root of 21220725 is about 276.8556594847.

Adding to 21220725 its reverse (52702212), we get a palindrome (73922937).

It can be divided in two parts, 21220 and 725, that added together give a triangular number (21945 = T₂₀₉).

The spelling of 21220725 in words is "twenty-one million, two hundred twenty thousand, seven hundred twenty-five".