21797661 has 4 divisors (see below), whose sum is σ = 29063552. Its totient is φ = 14531772.

The previous prime is 21797651. The next prime is 21797663. The reversal of 21797661 is 16679712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21797661 - 2⁶ = 21797597 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21797663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3632941 + ... + 3632946.

It is an arithmetic number, because the mean of its divisors is an integer number (7265888).

Almost surely, 2^21797661 is an apocalyptic number.

It is an amenable number.

21797661 is a deficient number, since it is larger than the sum of its proper divisors (7265891).

21797661 is an equidigital number, since it uses as much as digits as its factorization.

21797661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7265890.

The product of its digits is 31752, while the sum is 39.

The square root of 21797661 is about 4668.7965258726. The cubic root of 21797661 is about 279.3422528668.

The spelling of 21797661 in words is "twenty-one million, seven hundred ninety-seven thousand, six hundred sixty-one".