21661197 has 16 divisors (see below), whose sum is σ = 30528960. Its totient is φ = 13623552.

The previous prime is 21661183. The next prime is 21661223. The reversal of 21661197 is 79116612.

It is not a de Polignac number, because 21661197 - 2⁴ = 21661181 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21661097) 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, 16053 + ... + 17349.

It is an arithmetic number, because the mean of its divisors is an integer number (1908060).

Almost surely, 2^21661197 is an apocalyptic number.

It is an amenable number.

21661197 is a deficient number, since it is larger than the sum of its proper divisors (8867763).

21661197 is a wasteful number, since it uses less digits than its factorization.

21661197 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1612.

The product of its digits is 4536, while the sum is 33.

The square root of 21661197 is about 4654.1591077229. The cubic root of 21661197 is about 278.7580924943.

The spelling of 21661197 in words is "twenty-one million, six hundred sixty-one thousand, one hundred ninety-seven".