21772987 has 2 divisors, whose sum is σ = 21772988. Its totient is φ = 21772986.

The previous prime is 21772969. The next prime is 21773021. The reversal of 21772987 is 78927712.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21772987 - 2¹¹ = 21770939 is a prime.

It is not a weakly prime, because it can be changed into another prime (21772957) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10886493 + 10886494.

It is an arithmetic number, because the mean of its divisors is an integer number (10886494).

Almost surely, 2^21772987 is an apocalyptic number.

21772987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21772987 is an equidigital number, since it uses as much as digits as its factorization.

21772987 is an evil number, because the sum of its binary digits is even.

The product of its digits is 98784, while the sum is 43.

The square root of 21772987 is about 4666.1533408151. The cubic root of 21772987 is about 279.2368119964.

The spelling of 21772987 in words is "twenty-one million, seven hundred seventy-two thousand, nine hundred eighty-seven".