21321658 has 4 divisors (see below), whose sum is σ = 31982490. Its totient is φ = 10660828.

The previous prime is 21321647. The next prime is 21321661. The reversal of 21321658 is 85612312.

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

It can be written as a sum of positive squares in only one way, i.e., 15547249 + 5774409 = 3943^2 + 2403^2 .

It is a super-2 number, since 2×21321658² = 909226199737928, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5330413 + ... + 5330416.

Almost surely, 2^21321658 is an apocalyptic number.

21321658 is a deficient number, since it is larger than the sum of its proper divisors (10660832).

21321658 is a wasteful number, since it uses less digits than its factorization.

21321658 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10660831.

The product of its digits is 2880, while the sum is 28.

The square root of 21321658 is about 4617.5380886355. The cubic root of 21321658 is about 277.2939053575.

The spelling of 21321658 in words is "twenty-one million, three hundred twenty-one thousand, six hundred fifty-eight".