21689977 has 16 divisors (see below), whose sum is σ = 23647680. Its totient is φ = 19819008.

The previous prime is 21689971. The next prime is 21689981. The reversal of 21689977 is 77998612.

It is a happy number.

It is not a de Polignac number, because 21689977 - 2²³ = 13301369 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21689977.

It is not an unprimeable number, because it can be changed into a prime (21689971) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 155974 + ... + 156112.

It is an arithmetic number, because the mean of its divisors is an integer number (1477980).

Almost surely, 2^21689977 is an apocalyptic number.

21689977 is the 2329-th decagonal number.

It is an amenable number.

21689977 is a deficient number, since it is larger than the sum of its proper divisors (1957703).

21689977 is a wasteful number, since it uses less digits than its factorization.

21689977 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 360.

The product of its digits is 381024, while the sum is 49.

The square root of 21689977 is about 4657.2499396103. The cubic root of 21689977 is about 278.8814945304.

The spelling of 21689977 in words is "twenty-one million, six hundred eighty-nine thousand, nine hundred seventy-seven".