21091725 has 24 divisors (see below), whose sum is σ = 38747520. Its totient is φ = 11248560.

The previous prime is 21091717. The next prime is 21091727. The reversal of 21091725 is 52719012.

It is not a de Polignac number, because 21091725 - 2³ = 21091717 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21091727) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 14949 + ... + 16298.

It is an arithmetic number, because the mean of its divisors is an integer number (1614480).

Almost surely, 2^21091725 is an apocalyptic number.

21091725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21091725 is a deficient number, since it is larger than the sum of its proper divisors (17655795).

21091725 is a wasteful number, since it uses less digits than its factorization.

21091725 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31266 (or 31255 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 27.

The square root of 21091725 is about 4592.5728083505. The cubic root of 21091725 is about 276.2935204395.

The spelling of 21091725 in words is "twenty-one million, ninety-one thousand, seven hundred twenty-five".