21661395 has 16 divisors (see below), whose sum is σ = 39609600. Its totient is φ = 9902304.

The previous prime is 21661357. The next prime is 21661397. The reversal of 21661395 is 59316612.

It is a happy number.

It is not a de Polignac number, because 21661395 - 2¹¹ = 21659347 is a prime.

It is a plaindrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (21661397) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 103045 + ... + 103254.

It is an arithmetic number, because the mean of its divisors is an integer number (2475600).

Almost surely, 2^21661395 is an apocalyptic number.

21661395 is a deficient number, since it is larger than the sum of its proper divisors (17948205).

21661395 is a wasteful number, since it uses less digits than its factorization.

21661395 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 206314.

The product of its digits is 9720, while the sum is 33.

The square root of 21661395 is about 4654.1803789711. The cubic root of 21661395 is about 278.7589418462.

The spelling of 21661395 in words is "twenty-one million, six hundred sixty-one thousand, three hundred ninety-five".