20521377 has 16 divisors (see below), whose sum is σ = 30544000. Its totient is φ = 13617072.

The previous prime is 20521373. The next prime is 20521379. The reversal of 20521377 is 77312502.

It is not a de Polignac number, because 20521377 - 2² = 20521373 is a prime.

It is a super-2 number, since 2×20521377² = 842253827952258, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20521377.

It is not an unprimeable number, because it can be changed into a prime (20521373) 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, 4524 + ... + 7842.

It is an arithmetic number, because the mean of its divisors is an integer number (1909000).

Almost surely, 2^20521377 is an apocalyptic number.

20521377 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

20521377 is a deficient number, since it is larger than the sum of its proper divisors (10022623).

20521377 is a wasteful number, since it uses less digits than its factorization.

20521377 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3557 (or 3551 counting only the distinct ones).

The product of its (nonzero) digits is 2940, while the sum is 27.

The square root of 20521377 is about 4530.0526487007. The cubic root of 20521377 is about 273.7802818819.

Adding to 20521377 its reverse (77312502), we get a palindrome (97833879).

The spelling of 20521377 in words is "twenty million, five hundred twenty-one thousand, three hundred seventy-seven".