21377979 has 16 divisors (see below), whose sum is σ = 36195840. Its totient is φ = 12215880.

The previous prime is 21377969. The next prime is 21377981. The reversal of 21377979 is 97977312.

It is not a de Polignac number, because 21377979 - 2⁵ = 21377947 is a prime.

It is a super-2 number, since 2×21377979² = 914035972248882, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21377929) 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, 56367 + ... + 56744.

It is an arithmetic number, because the mean of its divisors is an integer number (2262240).

Almost surely, 2^21377979 is an apocalyptic number.

21377979 is a deficient number, since it is larger than the sum of its proper divisors (14817861).

21377979 is a wasteful number, since it uses less digits than its factorization.

21377979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 113127 (or 113121 counting only the distinct ones).

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

The square root of 21377979 is about 4623.6326627447. The cubic root of 21377979 is about 277.5378472849.

The spelling of 21377979 in words is "twenty-one million, three hundred seventy-seven thousand, nine hundred seventy-nine".