21653977 has 4 divisors (see below), whose sum is σ = 22793680. Its totient is φ = 20514276.

The previous prime is 21653959. The next prime is 21653987. The reversal of 21653977 is 77935612.

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-21653977 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21653927) 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, 569823 + ... + 569860.

It is an arithmetic number, because the mean of its divisors is an integer number (5698420).

Almost surely, 2^21653977 is an apocalyptic number.

It is an amenable number.

21653977 is a deficient number, since it is larger than the sum of its proper divisors (1139703).

21653977 is a wasteful number, since it uses less digits than its factorization.

21653977 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1139702.

The product of its digits is 79380, while the sum is 40.

The square root of 21653977 is about 4653.3833927584. The cubic root of 21653977 is about 278.7271176428.

The spelling of 21653977 in words is "twenty-one million, six hundred fifty-three thousand, nine hundred seventy-seven".