1621456551 has 24 divisors (see below), whose sum is σ = 2751564816. Its totient is φ = 907107840.

The previous prime is 1621456547. The next prime is 1621456579. The reversal of 1621456551 is 1556541261.

1621456551 is a `hidden beast` number, since 1 + 62 + 1 + 45 + 6 + 551 = 666.

It is not a de Polignac number, because 1621456551 - 2² = 1621456547 is a prime.

It is a super-3 number, since 3×1621456551³ (a number of 29 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1621456541) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 628650 + ... + 631223.

It is an arithmetic number, because the mean of its divisors is an integer number (114648534).

Almost surely, 2^1621456551 is an apocalyptic number.

1621456551 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1621456551 is a deficient number, since it is larger than the sum of its proper divisors (1130108265).

1621456551 is a wasteful number, since it uses less digits than its factorization.

1621456551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1259903 (or 1259900 counting only the distinct ones).

The product of its digits is 36000, while the sum is 36.

The square root of 1621456551 is about 40267.3136799564. The cubic root of 1621456551 is about 1174.8121748364.

The spelling of 1621456551 in words is "one billion, six hundred twenty-one million, four hundred fifty-six thousand, five hundred fifty-one".