21399777 has 12 divisors (see below), whose sum is σ = 35326720. Its totient is φ = 12228408.

The previous prime is 21399773. The next prime is 21399793. The reversal of 21399777 is 77799312.

It is not a de Polignac number, because 21399777 - 2² = 21399773 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21399773) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 169777 + ... + 169902.

Almost surely, 2^21399777 is an apocalyptic number.

It is an amenable number.

21399777 is a deficient number, since it is larger than the sum of its proper divisors (13926943).

21399777 is a wasteful number, since it uses less digits than its factorization.

21399777 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 339692 (or 339689 counting only the distinct ones).

The product of its digits is 166698, while the sum is 45.

The square root of 21399777 is about 4625.9892995985. The cubic root of 21399777 is about 277.6321454870.

The spelling of 21399777 in words is "twenty-one million, three hundred ninety-nine thousand, seven hundred seventy-seven".