21542890 has 16 divisors (see below), whose sum is σ = 38983680. Its totient is φ = 8571280.

The previous prime is 21542879. The next prime is 21542897. The reversal of 21542890 is 9824512.

It is a super-2 number, since 2×21542890² = 928192219104200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21542897) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3730 + ... + 7549.

It is an arithmetic number, because the mean of its divisors is an integer number (2436480).

Almost surely, 2^21542890 is an apocalyptic number.

21542890 is a deficient number, since it is larger than the sum of its proper divisors (17440790).

21542890 is a wasteful number, since it uses less digits than its factorization.

21542890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11477.

The product of its (nonzero) digits is 5760, while the sum is 31.

The square root of 21542890 is about 4641.4318911301. The cubic root of 21542890 is about 278.2496678823.

The spelling of 21542890 in words is "twenty-one million, five hundred forty-two thousand, eight hundred ninety".