21131725 has 12 divisors (see below), whose sum is σ = 26465940. Its totient is φ = 16736000.

The previous prime is 21131723. The next prime is 21131771. The reversal of 21131725 is 52713112.

It is a happy number.

It can be written as a sum of positive squares in 6 ways, for example, as 1471369 + 19660356 = 1213^2 + 4434^2 .

It is not a de Polignac number, because 21131725 - 2¹ = 21131723 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21131696 and 21131705.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21131723) 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, 1660 + ... + 6709.

It is an arithmetic number, because the mean of its divisors is an integer number (2205495).

Almost surely, 2^21131725 is an apocalyptic number.

21131725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21131725 is a deficient number, since it is larger than the sum of its proper divisors (5334215).

21131725 is a wasteful number, since it uses less digits than its factorization.

21131725 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8480 (or 8475 counting only the distinct ones).

The product of its digits is 420, while the sum is 22.

The square root of 21131725 is about 4596.9256030525. The cubic root of 21131725 is about 276.4680717024.

Adding to 21131725 its reverse (52713112), we get a palindrome (73844837).

The spelling of 21131725 in words is "twenty-one million, one hundred thirty-one thousand, seven hundred twenty-five".