21997925 has 6 divisors (see below), whose sum is σ = 27277458. Its totient is φ = 17598320.

The previous prime is 21997861. The next prime is 21997931. The reversal of 21997925 is 52979912.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 3602404 + 18395521 = 1898^2 + 4289^2 .

It is not a de Polignac number, because 21997925 - 2⁶ = 21997861 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 5 ways as a sum of consecutive naturals, for example, 439934 + ... + 439983.

It is an arithmetic number, because the mean of its divisors is an integer number (4546243).

Almost surely, 2^21997925 is an apocalyptic number.

21997925 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21997925 is a deficient number, since it is larger than the sum of its proper divisors (5279533).

21997925 is an equidigital number, since it uses as much as digits as its factorization.

21997925 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 879927 (or 879922 counting only the distinct ones).

The product of its digits is 102060, while the sum is 44.

The square root of 21997925 is about 4690.1945588643. The cubic root of 21997925 is about 280.1951233467.

It can be divided in two parts, 21997 and 925, that added together give a palindrome (22922).

The spelling of 21997925 in words is "twenty-one million, nine hundred ninety-seven thousand, nine hundred twenty-five".