21429725 has 12 divisors (see below), whose sum is σ = 26849844. Its totient is φ = 16965120.

The previous prime is 21429719. The next prime is 21429731. The reversal of 21429725 is 52792412.

It is an interprime number because it is at equal distance from previous prime (21429719) and next prime (21429731).

It can be written as a sum of positive squares in 6 ways, for example, as 972196 + 20457529 = 986^2 + 4523^2 .

It is not a de Polignac number, because 21429725 - 2¹⁸ = 21167581 is a prime.

It is a super-2 number, since 2×21429725² = 918466227151250, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21429691 and 21429700.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1994 + ... + 6843.

It is an arithmetic number, because the mean of its divisors is an integer number (2237487).

Almost surely, 2^21429725 is an apocalyptic number.

21429725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21429725 is a deficient number, since it is larger than the sum of its proper divisors (5420119).

21429725 is an equidigital number, since it uses as much as digits as its factorization.

21429725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8944 (or 8939 counting only the distinct ones).

The product of its digits is 10080, while the sum is 32.

The square root of 21429725 is about 4629.2250971410. The cubic root of 21429725 is about 277.7615962426.

The spelling of 21429725 in words is "twenty-one million, four hundred twenty-nine thousand, seven hundred twenty-five".