21771761 has 4 divisors (see below), whose sum is σ = 23751024. Its totient is φ = 19792500.

The previous prime is 21771749. The next prime is 21771787. The reversal of 21771761 is 16717712.

It is a happy number.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21771761 is a prime.

It is a super-2 number, since 2×21771761² = 948019154082242, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21771791) 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, 989615 + ... + 989636.

It is an arithmetic number, because the mean of its divisors is an integer number (5937756).

Almost surely, 2^21771761 is an apocalyptic number.

It is an amenable number.

21771761 is a deficient number, since it is larger than the sum of its proper divisors (1979263).

21771761 is a wasteful number, since it uses less digits than its factorization.

21771761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1979262.

The product of its digits is 4116, while the sum is 32.

The square root of 21771761 is about 4666.0219673722. The cubic root of 21771761 is about 279.2315707808.

The spelling of 21771761 in words is "twenty-one million, seven hundred seventy-one thousand, seven hundred sixty-one".