21770381 has 4 divisors (see below), whose sum is σ = 21811164. Its totient is φ = 21729600.

The previous prime is 21770363. The next prime is 21770407. The reversal of 21770381 is 18307712.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 4622500 + 17147881 = 2150^2 + 4141^2 .

It is a cyclic number.

It is not a de Polignac number, because 21770381 - 2⁶ = 21770317 is a prime.

It is a super-2 number, since 2×21770381² = 947898977770322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21770321) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19580 + ... + 20661.

It is an arithmetic number, because the mean of its divisors is an integer number (5452791).

Almost surely, 2^21770381 is an apocalyptic number.

It is an amenable number.

21770381 is a deficient number, since it is larger than the sum of its proper divisors (40783).

21770381 is an equidigital number, since it uses as much as digits as its factorization.

21770381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40782.

The product of its (nonzero) digits is 2352, while the sum is 29.

The square root of 21770381 is about 4665.8740874567. The cubic root of 21770381 is about 279.2256709715.

The spelling of 21770381 in words is "twenty-one million, seven hundred seventy thousand, three hundred eighty-one".