21642725 has 12 divisors (see below), whose sum is σ = 28901796. Its totient is φ = 15982080.

The previous prime is 21642667. The next prime is 21642727. The reversal of 21642725 is 52724612.

It is a happy number.

It can be written as a sum of positive squares in 6 ways, for example, as 3247204 + 18395521 = 1802^2 + 4289^2 .

It is not a de Polignac number, because 21642725 - 2¹⁰ = 21641701 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21642727) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 32972 + ... + 33621.

It is an arithmetic number, because the mean of its divisors is an integer number (2408483).

Almost surely, 2^21642725 is an apocalyptic number.

21642725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21642725 is a deficient number, since it is larger than the sum of its proper divisors (7259071).

21642725 is a wasteful number, since it uses less digits than its factorization.

21642725 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66616 (or 66611 counting only the distinct ones).

The product of its digits is 6720, while the sum is 29.

The square root of 21642725 is about 4652.1742228769. The cubic root of 21642725 is about 278.6788311947.

The spelling of 21642725 in words is "twenty-one million, six hundred forty-two thousand, seven hundred twenty-five".