21609977 has 2 divisors, whose sum is σ = 21609978. Its totient is φ = 21609976.

The previous prime is 21609953. The next prime is 21610003. The reversal of 21609977 is 77990612.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11215801 + 10394176 = 3349^2 + 3224^2 .

It is a cyclic number.

It is not a de Polignac number, because 21609977 - 2²⁴ = 4832761 is a prime.

It is a super-2 number, since 2×21609977² = 933982211881058, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21609937) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10804988 + 10804989.

It is an arithmetic number, because the mean of its divisors is an integer number (10804989).

Almost surely, 2^21609977 is an apocalyptic number.

It is an amenable number.

21609977 is a deficient number, since it is larger than the sum of its proper divisors (1).

21609977 is an equidigital number, since it uses as much as digits as its factorization.

21609977 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 47628, while the sum is 41.

The square root of 21609977 is about 4648.6532458337. The cubic root of 21609977 is about 278.5382022423.

The spelling of 21609977 in words is "twenty-one million, six hundred nine thousand, nine hundred seventy-seven".